diff --git a/fastboot/engine.cpp b/fastboot/engine.cpp
index 271b792..60b7124 100644
--- a/fastboot/engine.cpp
+++ b/fastboot/engine.cpp
@@ -27,7 +27,6 @@
  */
 
 #include "fastboot.h"
-#include "fs.h"
 
 #include <errno.h>
 #include <stdarg.h>
@@ -38,150 +37,117 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#define OP_DOWNLOAD   1
-#define OP_COMMAND    2
-#define OP_QUERY      3
-#define OP_NOTICE     4
-#define OP_DOWNLOAD_SPARSE 5
-#define OP_WAIT_FOR_DISCONNECT 6
-#define OP_DOWNLOAD_FD 7
-#define OP_UPLOAD 8
+#include <memory>
+#include <vector>
 
-typedef struct Action Action;
+#include <android-base/stringprintf.h>
 
-#define CMD_SIZE 64
-
-struct Action {
-    unsigned op;
-    Action* next;
-
-    char cmd[CMD_SIZE];
-    const char* prod;
-    void* data;
-    int fd;
-
-    // The protocol only supports 32-bit sizes, so you'll have to break
-    // anything larger into chunks.
-    uint32_t size;
-
-    const char *msg;
-    int (*func)(Action* a, int status, const char* resp);
-
-    double start;
+enum Op {
+    OP_DOWNLOAD,
+    OP_COMMAND,
+    OP_QUERY,
+    OP_NOTICE,
+    OP_DOWNLOAD_SPARSE,
+    OP_WAIT_FOR_DISCONNECT,
+    OP_DOWNLOAD_FD,
+    OP_UPLOAD,
 };
 
-static Action *action_list = 0;
-static Action *action_last = 0;
+struct Action {
+    Action(Op op, const std::string& cmd) : op(op), cmd(cmd) {}
 
+    Op op;
+    std::string cmd;
+    std::string msg;
 
+    std::string product;
 
+    void* data = nullptr;
+    // The protocol only supports 32-bit sizes, so you'll have to break
+    // anything larger into multiple chunks.
+    uint32_t size = 0;
+
+    int fd = -1;
+
+    int (*func)(Action& a, int status, const char* resp) = nullptr;
+
+    double start = -1;
+};
+
+static std::vector<std::unique_ptr<Action>> action_list;
 
 bool fb_getvar(Transport* transport, const std::string& key, std::string* value) {
-    std::string cmd = "getvar:";
-    cmd += key;
+    std::string cmd = "getvar:" + key;
 
     char buf[FB_RESPONSE_SZ + 1];
     memset(buf, 0, sizeof(buf));
-    if (fb_command_response(transport, cmd.c_str(), buf)) {
-      return false;
+    if (fb_command_response(transport, cmd, buf)) {
+        return false;
     }
     *value = buf;
     return true;
 }
 
-static int cb_default(Action* a, int status, const char* resp) {
+static int cb_default(Action& a, int status, const char* resp) {
     if (status) {
         fprintf(stderr,"FAILED (%s)\n", resp);
     } else {
         double split = now();
-        fprintf(stderr,"OKAY [%7.3fs]\n", (split - a->start));
-        a->start = split;
+        fprintf(stderr, "OKAY [%7.3fs]\n", (split - a.start));
+        a.start = split;
     }
     return status;
 }
 
-static Action *queue_action(unsigned op, const char *fmt, ...)
-{
-    va_list ap;
-    size_t cmdsize;
-
-    Action* a = reinterpret_cast<Action*>(calloc(1, sizeof(Action)));
-    if (a == nullptr) die("out of memory");
-
-    va_start(ap, fmt);
-    cmdsize = vsnprintf(a->cmd, sizeof(a->cmd), fmt, ap);
-    va_end(ap);
-
-    if (cmdsize >= sizeof(a->cmd)) {
-        free(a);
-        die("Command length (%zu) exceeds maximum size (%zu)", cmdsize, sizeof(a->cmd));
-    }
-
-    if (action_last) {
-        action_last->next = a;
-    } else {
-        action_list = a;
-    }
-    action_last = a;
-    a->op = op;
+static Action& queue_action(Op op, const std::string& cmd) {
+    std::unique_ptr<Action> a{new Action(op, cmd)};
     a->func = cb_default;
 
-    a->start = -1;
-
-    return a;
+    action_list.push_back(std::move(a));
+    return *action_list.back();
 }
 
-void fb_set_active(const char *slot)
-{
-    Action *a;
-    a = queue_action(OP_COMMAND, "set_active:%s", slot);
-    a->msg = mkmsg("Setting current slot to '%s'", slot);
+void fb_set_active(const std::string& slot) {
+    Action& a = queue_action(OP_COMMAND, "set_active:" + slot);
+    a.msg = "Setting current slot to '" + slot + "'...";
 }
 
-void fb_queue_erase(const char *ptn)
-{
-    Action *a;
-    a = queue_action(OP_COMMAND, "erase:%s", ptn);
-    a->msg = mkmsg("erasing '%s'", ptn);
+void fb_queue_erase(const std::string& partition) {
+    Action& a = queue_action(OP_COMMAND, "erase:" + partition);
+    a.msg = "Erasing '" + partition + "'...";
 }
 
-void fb_queue_flash_fd(const char *ptn, int fd, uint32_t sz)
-{
-    Action *a;
+void fb_queue_flash_fd(const std::string& partition, int fd, uint32_t sz) {
+    Action& a = queue_action(OP_DOWNLOAD_FD, "");
+    a.fd = fd;
+    a.size = sz;
+    a.msg = android::base::StringPrintf("Sending '%s' (%d KB)...", partition.c_str(), sz / 1024);
 
-    a = queue_action(OP_DOWNLOAD_FD, "");
-    a->fd = fd;
-    a->size = sz;
-    a->msg = mkmsg("sending '%s' (%d KB)", ptn, sz / 1024);
-
-    a = queue_action(OP_COMMAND, "flash:%s", ptn);
-    a->msg = mkmsg("writing '%s'", ptn);
+    Action& b = queue_action(OP_COMMAND, "flash:" + partition);
+    b.msg = "Writing '" + partition + "'...";
 }
 
-void fb_queue_flash(const char *ptn, void *data, uint32_t sz)
-{
-    Action *a;
+void fb_queue_flash(const std::string& partition, void* data, uint32_t sz) {
+    Action& a = queue_action(OP_DOWNLOAD, "");
+    a.data = data;
+    a.size = sz;
+    a.msg = android::base::StringPrintf("Sending '%s' (%d KB)...", partition.c_str(), sz / 1024);
 
-    a = queue_action(OP_DOWNLOAD, "");
-    a->data = data;
-    a->size = sz;
-    a->msg = mkmsg("sending '%s' (%d KB)", ptn, sz / 1024);
-
-    a = queue_action(OP_COMMAND, "flash:%s", ptn);
-    a->msg = mkmsg("writing '%s'", ptn);
+    Action& b = queue_action(OP_COMMAND, "flash:" + partition);
+    b.msg = "Writing '" + partition + "'...";
 }
 
-void fb_queue_flash_sparse(const char* ptn, struct sparse_file* s, uint32_t sz, size_t current,
-                           size_t total) {
-    Action *a;
+void fb_queue_flash_sparse(const std::string& partition, struct sparse_file* s, uint32_t sz,
+                           size_t current, size_t total) {
+    Action& a = queue_action(OP_DOWNLOAD_SPARSE, "");
+    a.data = s;
+    a.size = 0;
+    a.msg = android::base::StringPrintf("Sending sparse '%s' %zu/%zu (%d KB)...", partition.c_str(),
+                                        current, total, sz / 1024);
 
-    a = queue_action(OP_DOWNLOAD_SPARSE, "");
-    a->data = s;
-    a->size = 0;
-    a->msg = mkmsg("sending sparse '%s' %zu/%zu (%d KB)", ptn, current, total, sz / 1024);
-
-    a = queue_action(OP_COMMAND, "flash:%s", ptn);
-    a->msg = mkmsg("writing '%s' %zu/%zu", ptn, current, total);
+    Action& b = queue_action(OP_COMMAND, "flash:" + partition);
+    b.msg =
+        android::base::StringPrintf("Writing '%s' %zu/%zu...", partition.c_str(), current, total);
 }
 
 static int match(const char* str, const char** value, unsigned count) {
@@ -205,212 +171,181 @@
     return 0;
 }
 
-
-
-static int cb_check(Action* a, int status, const char* resp, int invert)
-{
-    const char** value = reinterpret_cast<const char**>(a->data);
-    unsigned count = a->size;
+static int cb_check(Action& a, int status, const char* resp, int invert) {
+    const char** value = reinterpret_cast<const char**>(a.data);
+    unsigned count = a.size;
     unsigned n;
-    int yes;
 
     if (status) {
         fprintf(stderr,"FAILED (%s)\n", resp);
         return status;
     }
 
-    if (a->prod) {
-        if (strcmp(a->prod, cur_product) != 0) {
+    if (!a.product.empty()) {
+        if (a.product != cur_product) {
             double split = now();
-            fprintf(stderr,"IGNORE, product is %s required only for %s [%7.3fs]\n",
-                    cur_product, a->prod, (split - a->start));
-            a->start = split;
+            fprintf(stderr, "IGNORE, product is %s required only for %s [%7.3fs]\n", cur_product,
+                    a.product.c_str(), (split - a.start));
+            a.start = split;
             return 0;
         }
     }
 
-    yes = match(resp, value, count);
+    int yes = match(resp, value, count);
     if (invert) yes = !yes;
 
     if (yes) {
         double split = now();
-        fprintf(stderr,"OKAY [%7.3fs]\n", (split - a->start));
-        a->start = split;
+        fprintf(stderr, "OKAY [%7.3fs]\n", (split - a.start));
+        a.start = split;
         return 0;
     }
 
-    fprintf(stderr,"FAILED\n\n");
-    fprintf(stderr,"Device %s is '%s'.\n", a->cmd + 7, resp);
-    fprintf(stderr,"Update %s '%s'",
-            invert ? "rejects" : "requires", value[0]);
+    fprintf(stderr, "FAILED\n\n");
+    fprintf(stderr, "Device %s is '%s'.\n", a.cmd.c_str() + 7, resp);
+    fprintf(stderr, "Update %s '%s'", invert ? "rejects" : "requires", value[0]);
     for (n = 1; n < count; n++) {
-        fprintf(stderr," or '%s'", value[n]);
+        fprintf(stderr, " or '%s'", value[n]);
     }
-    fprintf(stderr,".\n\n");
+    fprintf(stderr, ".\n\n");
     return -1;
 }
 
-static int cb_require(Action*a, int status, const char* resp) {
+static int cb_require(Action& a, int status, const char* resp) {
     return cb_check(a, status, resp, 0);
 }
 
-static int cb_reject(Action* a, int status, const char* resp) {
+static int cb_reject(Action& a, int status, const char* resp) {
     return cb_check(a, status, resp, 1);
 }
 
-static char* xstrdup(const char* s) {
-    char* result = strdup(s);
-    if (!result) die("out of memory");
-    return result;
+void fb_queue_require(const std::string& product, const std::string& var, bool invert,
+                      size_t nvalues, const char** values) {
+    Action& a = queue_action(OP_QUERY, "getvar:" + var);
+    a.product = product;
+    a.data = values;
+    a.size = nvalues;
+    a.msg = "Checking " + var;
+    a.func = invert ? cb_reject : cb_require;
+    if (a.data == nullptr) die("out of memory");
 }
 
-void fb_queue_require(const char *prod, const char *var,
-                      bool invert, size_t nvalues, const char **value)
-{
-    Action *a;
-    a = queue_action(OP_QUERY, "getvar:%s", var);
-    a->prod = prod;
-    a->data = value;
-    a->size = nvalues;
-    a->msg = mkmsg("checking %s", var);
-    a->func = invert ? cb_reject : cb_require;
-    if (a->data == nullptr) die("out of memory");
-}
-
-static int cb_display(Action* a, int status, const char* resp) {
+static int cb_display(Action& a, int status, const char* resp) {
     if (status) {
-        fprintf(stderr, "%s FAILED (%s)\n", a->cmd, resp);
+        fprintf(stderr, "%s FAILED (%s)\n", a.cmd.c_str(), resp);
         return status;
     }
-    fprintf(stderr, "%s: %s\n", static_cast<const char*>(a->data), resp);
-    free(static_cast<char*>(a->data));
+    fprintf(stderr, "%s: %s\n", static_cast<const char*>(a.data), resp);
+    free(static_cast<char*>(a.data));
     return 0;
 }
 
-void fb_queue_display(const char* var, const char* prettyname) {
-    Action* a = queue_action(OP_QUERY, "getvar:%s", var);
-    a->data = xstrdup(prettyname);
-    a->func = cb_display;
+void fb_queue_display(const std::string& label, const std::string& var) {
+    Action& a = queue_action(OP_QUERY, "getvar:" + var);
+    a.data = xstrdup(label.c_str());
+    a.func = cb_display;
 }
 
-static int cb_save(Action* a, int status, const char* resp) {
+static int cb_save(Action& a, int status, const char* resp) {
     if (status) {
-        fprintf(stderr, "%s FAILED (%s)\n", a->cmd, resp);
+        fprintf(stderr, "%s FAILED (%s)\n", a.cmd.c_str(), resp);
         return status;
     }
-    strncpy(reinterpret_cast<char*>(a->data), resp, a->size);
+    strncpy(reinterpret_cast<char*>(a.data), resp, a.size);
     return 0;
 }
 
-void fb_queue_query_save(const char* var, char* dest, uint32_t dest_size) {
-    Action* a = queue_action(OP_QUERY, "getvar:%s", var);
-    a->data = dest;
-    a->size = dest_size;
-    a->func = cb_save;
+void fb_queue_query_save(const std::string& var, char* dest, uint32_t dest_size) {
+    Action& a = queue_action(OP_QUERY, "getvar:" + var);
+    a.data = dest;
+    a.size = dest_size;
+    a.func = cb_save;
 }
 
-static int cb_do_nothing(Action*, int , const char*) {
-    fprintf(stderr,"\n");
+static int cb_do_nothing(Action&, int, const char*) {
+    fprintf(stderr, "\n");
     return 0;
 }
 
-void fb_queue_reboot(void)
-{
-    Action *a = queue_action(OP_COMMAND, "reboot");
-    a->func = cb_do_nothing;
-    a->msg = "rebooting";
+void fb_queue_reboot() {
+    Action& a = queue_action(OP_COMMAND, "reboot");
+    a.func = cb_do_nothing;
+    a.msg = "Rebooting...";
 }
 
-void fb_queue_command(const char *cmd, const char *msg)
-{
-    Action *a = queue_action(OP_COMMAND, cmd);
-    a->msg = msg;
+void fb_queue_command(const std::string& cmd, const std::string& msg) {
+    Action& a = queue_action(OP_COMMAND, cmd);
+    a.msg = msg;
 }
 
-void fb_queue_download(const char *name, void *data, uint32_t size)
-{
-    Action *a = queue_action(OP_DOWNLOAD, "");
-    a->data = data;
-    a->size = size;
-    a->msg = mkmsg("downloading '%s'", name);
+void fb_queue_download(const std::string& name, void* data, uint32_t size) {
+    Action& a = queue_action(OP_DOWNLOAD, "");
+    a.data = data;
+    a.size = size;
+    a.msg = "Downloading '" + name + "'";
 }
 
-void fb_queue_download_fd(const char *name, int fd, uint32_t sz)
-{
-    Action *a;
-    a = queue_action(OP_DOWNLOAD_FD, "");
-    a->fd = fd;
-    a->size = sz;
-    a->msg = mkmsg("sending '%s' (%d KB)", name, sz / 1024);
+void fb_queue_download_fd(const std::string& name, int fd, uint32_t sz) {
+    Action& a = queue_action(OP_DOWNLOAD_FD, "");
+    a.fd = fd;
+    a.size = sz;
+    a.msg = android::base::StringPrintf("Sending '%s' (%d KB)", name.c_str(), sz / 1024);
 }
 
-void fb_queue_upload(const char* outfile) {
-    Action* a = queue_action(OP_UPLOAD, "");
-    a->data = xstrdup(outfile);
-    a->msg = mkmsg("uploading '%s'", outfile);
+void fb_queue_upload(const std::string& outfile) {
+    Action& a = queue_action(OP_UPLOAD, "");
+    a.data = xstrdup(outfile.c_str());
+    a.msg = "Uploading '" + outfile + "'";
 }
 
-void fb_queue_notice(const char* notice) {
-    Action *a = queue_action(OP_NOTICE, "");
-    a->data = (void*) notice;
+void fb_queue_notice(const std::string& notice) {
+    Action& a = queue_action(OP_NOTICE, "");
+    a.msg = notice;
 }
 
-void fb_queue_wait_for_disconnect(void)
-{
+void fb_queue_wait_for_disconnect() {
     queue_action(OP_WAIT_FOR_DISCONNECT, "");
 }
 
-int64_t fb_execute_queue(Transport* transport)
-{
-    Action *a;
-    char resp[FB_RESPONSE_SZ+1];
+int64_t fb_execute_queue(Transport* transport) {
     int64_t status = 0;
-
-    a = action_list;
-    if (!a)
-        return status;
-    resp[FB_RESPONSE_SZ] = 0;
-
-    double start = -1;
-    for (a = action_list; a; a = a->next) {
+    for (auto& a : action_list) {
         a->start = now();
-        if (start < 0) start = a->start;
-        if (a->msg) {
-            // fprintf(stderr,"%30s... ",a->msg);
-            fprintf(stderr,"%s...\n",a->msg);
+        if (!a->msg.empty()) {
+            fprintf(stderr, "%s\n", a->msg.c_str());
         }
         if (a->op == OP_DOWNLOAD) {
             status = fb_download_data(transport, a->data, a->size);
-            status = a->func(a, status, status ? fb_get_error().c_str() : "");
+            status = a->func(*a, status, status ? fb_get_error().c_str() : "");
             if (status) break;
         } else if (a->op == OP_DOWNLOAD_FD) {
             status = fb_download_data_fd(transport, a->fd, a->size);
-            status = a->func(a, status, status ? fb_get_error().c_str() : "");
+            status = a->func(*a, status, status ? fb_get_error().c_str() : "");
             if (status) break;
         } else if (a->op == OP_COMMAND) {
             status = fb_command(transport, a->cmd);
-            status = a->func(a, status, status ? fb_get_error().c_str() : "");
+            status = a->func(*a, status, status ? fb_get_error().c_str() : "");
             if (status) break;
         } else if (a->op == OP_QUERY) {
+            char resp[FB_RESPONSE_SZ + 1] = {};
             status = fb_command_response(transport, a->cmd, resp);
-            status = a->func(a, status, status ? fb_get_error().c_str() : resp);
+            status = a->func(*a, status, status ? fb_get_error().c_str() : resp);
             if (status) break;
         } else if (a->op == OP_NOTICE) {
-            fprintf(stderr,"%s\n",(char*)a->data);
+            // We already showed the notice because it's in `Action::msg`.
         } else if (a->op == OP_DOWNLOAD_SPARSE) {
             status = fb_download_data_sparse(transport, reinterpret_cast<sparse_file*>(a->data));
-            status = a->func(a, status, status ? fb_get_error().c_str() : "");
+            status = a->func(*a, status, status ? fb_get_error().c_str() : "");
             if (status) break;
         } else if (a->op == OP_WAIT_FOR_DISCONNECT) {
             transport->WaitForDisconnect();
         } else if (a->op == OP_UPLOAD) {
             status = fb_upload_data(transport, reinterpret_cast<char*>(a->data));
-            status = a->func(a, status, status ? fb_get_error().c_str() : "");
+            status = a->func(*a, status, status ? fb_get_error().c_str() : "");
         } else {
-            die("bogus action");
+            die("unknown action: %d", a->op);
         }
     }
-
-    fprintf(stderr,"finished. total time: %.3fs\n", (now() - start));
+    action_list.clear();
     return status;
 }
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 7155b7e..237f081 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -635,27 +635,31 @@
     return fd.release();
 }
 
-static char *strip(char *s)
-{
-    int n;
-    while(*s && isspace(*s)) s++;
-    n = strlen(s);
-    while(n-- > 0) {
-        if(!isspace(s[n])) break;
+static char* strip(char* s) {
+    while (*s && isspace(*s)) s++;
+
+    int n = strlen(s);
+    while (n-- > 0) {
+        if (!isspace(s[n])) break;
         s[n] = 0;
     }
     return s;
 }
 
 #define MAX_OPTIONS 32
-static int setup_requirement_line(char *name)
-{
+static void check_requirement(Transport* transport, char* line) {
     char *val[MAX_OPTIONS];
-    char *prod = nullptr;
-    unsigned n, count;
+    unsigned count;
     char *x;
     int invert = 0;
 
+    // "require product=alpha|beta|gamma"
+    // "require version-bootloader=1234"
+    // "require-for-product:gamma version-bootloader=istanbul|constantinople"
+    // "require partition-exists=vendor"
+
+    char* name = line;
+    const char* product = "";
     if (!strncmp(name, "reject ", 7)) {
         name += 7;
         invert = 1;
@@ -664,19 +668,46 @@
         invert = 0;
     } else if (!strncmp(name, "require-for-product:", 20)) {
         // Get the product and point name past it
-        prod = name + 20;
+        product = name + 20;
         name = strchr(name, ' ');
-        if (!name) return -1;
+        if (!name) die("android-info.txt syntax error: %s", line);
         *name = 0;
         name += 1;
         invert = 0;
     }
 
     x = strchr(name, '=');
-    if (x == 0) return 0;
+    if (x == 0) return;
     *x = 0;
     val[0] = x + 1;
 
+    name = strip(name);
+
+    // "require partition-exists=x" is a special case, added because of the trouble we had when
+    // Pixel 2 shipped with new partitions and users used old versions of fastboot to flash them,
+    // missing out new partitions. A device with new partitions can use "partition-exists" to
+    // override the `is_optional` field in the `images` array.
+    if (!strcmp(name, "partition-exists")) {
+        const char* partition_name = val[0];
+        std::string has_slot;
+        if (!fb_getvar(transport, std::string("has-slot:") + partition_name, &has_slot) ||
+            (has_slot != "yes" && has_slot != "no")) {
+            die("device doesn't have required partition %s!", partition_name);
+        }
+        bool known_partition = false;
+        for (size_t i = 0; i < arraysize(images); ++i) {
+            if (images[i].nickname && !strcmp(images[i].nickname, partition_name)) {
+                images[i].is_optional = false;
+                known_partition = true;
+            }
+        }
+        if (!known_partition) {
+            die("device requires partition %s which is not known to this version of fastboot",
+                partition_name);
+        }
+        return;
+    }
+
     for(count = 1; count < MAX_OPTIONS; count++) {
         x = strchr(val[count - 1],'|');
         if (x == 0) break;
@@ -684,54 +715,39 @@
         val[count] = x + 1;
     }
 
-    name = strip(name);
-    for(n = 0; n < count; n++) val[n] = strip(val[n]);
-
-    name = strip(name);
-    if (name == 0) return -1;
-
-    const char* var = name;
     // Work around an unfortunate name mismatch.
-    if (!strcmp(name,"board")) var = "product";
+    const char* var = name;
+    if (!strcmp(name, "board")) var = "product";
 
     const char** out = reinterpret_cast<const char**>(malloc(sizeof(char*) * count));
-    if (out == 0) return -1;
+    if (out == nullptr) die("out of memory");
 
-    for(n = 0; n < count; n++) {
-        out[n] = strdup(strip(val[n]));
-        if (out[n] == 0) {
-            for(size_t i = 0; i < n; ++i) {
-                free((char*) out[i]);
-            }
-            free(out);
-            return -1;
-        }
+    for (size_t i = 0; i < count; ++i) {
+        out[i] = xstrdup(strip(val[i]));
     }
 
-    fb_queue_require(prod, var, invert, n, out);
-    return 0;
+    fb_queue_require(product, var, invert, count, out);
 }
 
-static void setup_requirements(char* data, int64_t sz) {
+static void check_requirements(Transport* transport, char* data, int64_t sz) {
     char* s = data;
     while (sz-- > 0) {
         if (*s == '\n') {
             *s++ = 0;
-            if (setup_requirement_line(data)) {
-                die("out of memory");
-            }
+            check_requirement(transport, data);
             data = s;
         } else {
             s++;
         }
     }
+    if (fb_execute_queue(transport)) die("requirements not met!");
 }
 
 static void queue_info_dump() {
     fb_queue_notice("--------------------------------------------");
-    fb_queue_display("version-bootloader", "Bootloader Version...");
-    fb_queue_display("version-baseband",   "Baseband Version.....");
-    fb_queue_display("serialno",           "Serial Number........");
+    fb_queue_display("Bootloader Version...", "version-bootloader");
+    fb_queue_display("Baseband Version.....", "version-baseband");
+    fb_queue_display("Serial Number........", "serialno");
     fb_queue_notice("--------------------------------------------");
 }
 
@@ -891,14 +907,13 @@
     lseek(fd, 0, SEEK_SET);
 }
 
-static void flash_buf(const char *pname, struct fastboot_buffer *buf)
+static void flash_buf(const std::string& partition, struct fastboot_buffer *buf)
 {
     sparse_file** s;
 
     // Rewrite vbmeta if that's what we're flashing and modification has been requested.
     if ((g_disable_verity || g_disable_verification) &&
-        (strcmp(pname, "vbmeta") == 0 || strcmp(pname, "vbmeta_a") == 0 ||
-         strcmp(pname, "vbmeta_b") == 0)) {
+        (partition == "vbmeta" || partition == "vbmeta_a" || partition == "vbmeta_b")) {
         rewrite_vbmeta_buffer(buf);
     }
 
@@ -914,12 +929,12 @@
 
             for (size_t i = 0; i < sparse_files.size(); ++i) {
                 const auto& pair = sparse_files[i];
-                fb_queue_flash_sparse(pname, pair.first, pair.second, i + 1, sparse_files.size());
+                fb_queue_flash_sparse(partition, pair.first, pair.second, i + 1, sparse_files.size());
             }
             break;
         }
         case FB_BUFFER_FD:
-            fb_queue_flash_fd(pname, buf->fd, buf->sz);
+            fb_queue_flash_fd(partition, buf->fd, buf->sz);
             break;
         default:
             die("unknown buffer type: %d", buf->type);
@@ -1117,11 +1132,11 @@
         }
     }
     if (slot_override != "") {
-        fb_set_active((separator + slot_override).c_str());
+        fb_set_active(separator + slot_override);
     } else {
         std::string current_slot = get_current_slot(transport);
         if (current_slot != "") {
-            fb_set_active((separator + current_slot).c_str());
+            fb_set_active(separator + current_slot);
         }
     }
 }
@@ -1143,7 +1158,7 @@
         die("update package '%s' has no android-info.txt", filename);
     }
 
-    setup_requirements(reinterpret_cast<char*>(data), sz);
+    check_requirements(transport, reinterpret_cast<char*>(data), sz);
 
     std::string secondary;
     if (!skip_secondary) {
@@ -1185,7 +1200,7 @@
         auto update = [&](const std::string& partition) {
             do_update_signature(zip, images[i].sig_name);
             if (erase_first && needs_erase(transport, partition.c_str())) {
-                fb_queue_erase(partition.c_str());
+                fb_queue_erase(partition);
             }
             flash_buf(partition.c_str(), &buf);
             /* not closing the fd here since the sparse code keeps the fd around
@@ -1232,7 +1247,7 @@
     void* data = load_file(fname.c_str(), &sz);
     if (data == nullptr) die("could not load android-info.txt: %s", strerror(errno));
 
-    setup_requirements(reinterpret_cast<char*>(data), sz);
+    check_requirements(transport, reinterpret_cast<char*>(data), sz);
 
     std::string secondary;
     if (!skip_secondary) {
@@ -1267,7 +1282,7 @@
         auto flashall = [&](const std::string &partition) {
             do_send_signature(fname.c_str());
             if (erase_first && needs_erase(transport, partition.c_str())) {
-                fb_queue_erase(partition.c_str());
+                fb_queue_erase(partition);
             }
             flash_buf(partition.c_str(), &buf);
         };
@@ -1307,7 +1322,7 @@
     while (!args->empty()) {
         command += " " + next_arg(args);
     }
-    fb_queue_command(command.c_str(), "");
+    fb_queue_command(command, "");
 }
 
 static int64_t parse_num(const char *arg)
@@ -1362,8 +1377,8 @@
 
 static unsigned fb_get_flash_block_size(Transport* transport, std::string name) {
     std::string sizeString;
-    if (!fb_getvar(transport, name.c_str(), &sizeString) || sizeString.empty()) {
-        /* This device does not report flash block sizes, so return 0 */
+    if (!fb_getvar(transport, name, &sizeString) || sizeString.empty()) {
+        // This device does not report flash block sizes, so return 0.
         return 0;
     }
     sizeString = fb_fix_numeric_var(sizeString);
@@ -1381,7 +1396,7 @@
 }
 
 static void fb_perform_format(Transport* transport,
-                              const char* partition, int skip_if_not_supported,
+                              const std::string& partition, int skip_if_not_supported,
                               const std::string& type_override, const std::string& size_override,
                               const std::string& initial_dir) {
     std::string partition_type, partition_size;
@@ -1400,26 +1415,26 @@
         limit = sparse_limit;
     }
 
-    if (!fb_getvar(transport, std::string("partition-type:") + partition, &partition_type)) {
+    if (!fb_getvar(transport, "partition-type:" + partition, &partition_type)) {
         errMsg = "Can't determine partition type.\n";
         goto failed;
     }
     if (!type_override.empty()) {
         if (partition_type != type_override) {
             fprintf(stderr, "Warning: %s type is %s, but %s was requested for formatting.\n",
-                    partition, partition_type.c_str(), type_override.c_str());
+                    partition.c_str(), partition_type.c_str(), type_override.c_str());
         }
         partition_type = type_override;
     }
 
-    if (!fb_getvar(transport, std::string("partition-size:") + partition, &partition_size)) {
+    if (!fb_getvar(transport, "partition-size:" + partition, &partition_size)) {
         errMsg = "Unable to get partition size\n";
         goto failed;
     }
     if (!size_override.empty()) {
         if (partition_size != size_override) {
             fprintf(stderr, "Warning: %s size is %s, but %s was requested for formatting.\n",
-                    partition, partition_size.c_str(), size_override.c_str());
+                    partition.c_str(), partition_size.c_str(), size_override.c_str());
         }
         partition_size = size_override;
     }
@@ -1449,7 +1464,7 @@
 
     if (fs_generator_generate(gen, output.path, size, initial_dir,
             eraseBlkSize, logicalBlkSize)) {
-        die("Cannot generate image for %s", partition);
+        die("Cannot generate image for %s", partition.c_str());
         return;
     }
 
@@ -1632,6 +1647,8 @@
         return 1;
     }
 
+    const double start = now();
+
     if (!supports_AB(transport) && supports_AB_obsolete(transport)) {
         fprintf(stderr, "Warning: Device A/B support is outdated. Bootloader update required.\n");
     }
@@ -1659,7 +1676,7 @@
 
         if (command == "getvar") {
             std::string variable = next_arg(&args);
-            fb_queue_display(variable.c_str(), variable.c_str());
+            fb_queue_display(variable, variable);
         } else if (command == "erase") {
             std::string partition = next_arg(&args);
             auto erase = [&](const std::string& partition) {
@@ -1671,7 +1688,7 @@
                             partition_type.c_str());
                 }
 
-                fb_queue_erase(partition.c_str());
+                fb_queue_erase(partition);
             };
             do_for_partitions(transport, partition, slot_override, erase, true);
         } else if (android::base::StartsWith(command, "format")) {
@@ -1692,10 +1709,9 @@
 
             auto format = [&](const std::string& partition) {
                 if (erase_first && needs_erase(transport, partition.c_str())) {
-                    fb_queue_erase(partition.c_str());
+                    fb_queue_erase(partition);
                 }
-                fb_perform_format(transport, partition.c_str(), 0, type_override, size_override,
-                                  "");
+                fb_perform_format(transport, partition, 0, type_override, size_override, "");
             };
             do_for_partitions(transport, partition.c_str(), slot_override, format, true);
         } else if (command == "signature") {
@@ -1749,7 +1765,7 @@
 
             auto flash = [&](const std::string &partition) {
                 if (erase_first && needs_erase(transport, partition.c_str())) {
-                    fb_queue_erase(partition.c_str());
+                    fb_queue_erase(partition);
                 }
                 do_flash(transport, partition.c_str(), fname.c_str());
             };
@@ -1764,7 +1780,7 @@
 
             data = load_bootable_image(kernel, ramdisk, second_stage, &sz, cmdline);
             auto flashraw = [&](const std::string& partition) {
-                fb_queue_flash(partition.c_str(), data, sz);
+                fb_queue_flash(partition, data, sz);
             };
             do_for_partitions(transport, partition, slot_override, flashraw, true);
         } else if (command == "flashall") {
@@ -1798,7 +1814,7 @@
                     fb_getvar(transport, "slot-suffixes", &var)) {
                 slot = "_" + slot;
             }
-            fb_set_active(slot.c_str());
+            fb_set_active(slot);
         } else if (command == "stage") {
             std::string filename = next_arg(&args);
 
@@ -1806,10 +1822,10 @@
             if (!load_buf(transport, filename.c_str(), &buf) || buf.type != FB_BUFFER_FD) {
                 die("cannot load '%s'", filename.c_str());
             }
-            fb_queue_download_fd(filename.c_str(), buf.fd, buf.sz);
+            fb_queue_download_fd(filename, buf.fd, buf.sz);
         } else if (command == "get_staged") {
             std::string filename = next_arg(&args);
-            fb_queue_upload(filename.c_str());
+            fb_queue_upload(filename);
         } else if (command == "oem") {
             do_oem_command("oem", &args);
         } else if (command == "flashing") {
@@ -1855,7 +1871,7 @@
         }
     }
     if (wants_set_active) {
-        fb_set_active(next_active.c_str());
+        fb_set_active(next_active);
     }
     if (wants_reboot && !skip_reboot) {
         fb_queue_reboot();
@@ -1868,5 +1884,7 @@
         fb_queue_wait_for_disconnect();
     }
 
-    return fb_execute_queue(transport) ? EXIT_FAILURE : EXIT_SUCCESS;
+    int status = fb_execute_queue(transport) ? EXIT_FAILURE : EXIT_SUCCESS;
+    fprintf(stderr, "Finished. Total time: %.3fs\n", (now() - start));
+    return status;
 }
diff --git a/fastboot/fastboot.h b/fastboot/fastboot.h
index f4faa21..a31057a 100644
--- a/fastboot/fastboot.h
+++ b/fastboot/fastboot.h
@@ -39,8 +39,8 @@
 struct sparse_file;
 
 /* protocol.c - fastboot protocol */
-int fb_command(Transport* transport, const char* cmd);
-int fb_command_response(Transport* transport, const char* cmd, char* response);
+int fb_command(Transport* transport, const std::string& cmd);
+int fb_command_response(Transport* transport, const std::string& cmd, char* response);
 int64_t fb_download_data(Transport* transport, const void* data, uint32_t size);
 int64_t fb_download_data_fd(Transport* transport, int fd, uint32_t size);
 int fb_download_data_sparse(Transport* transport, struct sparse_file* s);
@@ -52,29 +52,29 @@
 
 /* engine.c - high level command queue engine */
 bool fb_getvar(Transport* transport, const std::string& key, std::string* value);
-void fb_queue_flash(const char *ptn, void *data, uint32_t sz);
-void fb_queue_flash_fd(const char *ptn, int fd, uint32_t sz);
-void fb_queue_flash_sparse(const char* ptn, struct sparse_file* s, uint32_t sz, size_t current,
-                           size_t total);
-void fb_queue_erase(const char *ptn);
-void fb_queue_format(const char *ptn, int skip_if_not_supported, int32_t max_chunk_sz);
-void fb_queue_require(const char *prod, const char *var, bool invert,
-                      size_t nvalues, const char **value);
-void fb_queue_display(const char *var, const char *prettyname);
-void fb_queue_query_save(const char *var, char *dest, uint32_t dest_size);
+void fb_queue_flash(const std::string& partition, void* data, uint32_t sz);
+void fb_queue_flash_fd(const std::string& partition, int fd, uint32_t sz);
+void fb_queue_flash_sparse(const std::string& partition, struct sparse_file* s, uint32_t sz,
+                           size_t current, size_t total);
+void fb_queue_erase(const std::string& partition);
+void fb_queue_format(const std::string& partition, int skip_if_not_supported, int32_t max_chunk_sz);
+void fb_queue_require(const std::string& prod, const std::string& var, bool invert, size_t nvalues,
+                      const char** values);
+void fb_queue_display(const std::string& label, const std::string& var);
+void fb_queue_query_save(const std::string& var, char* dest, uint32_t dest_size);
 void fb_queue_reboot(void);
-void fb_queue_command(const char *cmd, const char *msg);
-void fb_queue_download(const char *name, void *data, uint32_t size);
-void fb_queue_download_fd(const char *name, int fd, uint32_t sz);
-void fb_queue_upload(const char* outfile);
-void fb_queue_notice(const char *notice);
+void fb_queue_command(const std::string& cmd, const std::string& msg);
+void fb_queue_download(const std::string& name, void* data, uint32_t size);
+void fb_queue_download_fd(const std::string& name, int fd, uint32_t sz);
+void fb_queue_upload(const std::string& outfile);
+void fb_queue_notice(const std::string& notice);
 void fb_queue_wait_for_disconnect(void);
 int64_t fb_execute_queue(Transport* transport);
-void fb_set_active(const char *slot);
+void fb_set_active(const std::string& slot);
 
 /* util stuff */
 double now();
-char *mkmsg(const char *fmt, ...);
+char* xstrdup(const char*);
 
 // These printf-like functions are implemented in terms of vsnprintf, so they
 // use the same attribute for compile-time format string checking. On Windows,
diff --git a/fastboot/protocol.cpp b/fastboot/protocol.cpp
index dcdf8f0..c239861 100644
--- a/fastboot/protocol.cpp
+++ b/fastboot/protocol.cpp
@@ -113,10 +113,10 @@
     return -1;
 }
 
-static int64_t _command_start(Transport* transport, const char* cmd, uint32_t size, char* response) {
-    size_t cmdsize = strlen(cmd);
-    if (cmdsize > 64) {
-        g_error = android::base::StringPrintf("command too large (%zu)", cmdsize);
+static int64_t _command_start(Transport* transport, const std::string& cmd, uint32_t size,
+                              char* response) {
+    if (cmd.size() > 64) {
+        g_error = android::base::StringPrintf("command too large (%zu)", cmd.size());
         return -1;
     }
 
@@ -124,7 +124,7 @@
         response[0] = 0;
     }
 
-    if (transport->Write(cmd, cmdsize) != static_cast<int>(cmdsize)) {
+    if (transport->Write(cmd.c_str(), cmd.size()) != static_cast<int>(cmd.size())) {
         g_error = android::base::StringPrintf("command write failed (%s)", strerror(errno));
         transport->Close();
         return -1;
@@ -167,8 +167,8 @@
     return check_response(transport, 0, 0) < 0 ? -1 : 0;
 }
 
-static int64_t _command_send(Transport* transport, const char* cmd, const void* data, uint32_t size,
-                         char* response) {
+static int64_t _command_send(Transport* transport, const std::string& cmd, const void* data,
+                             uint32_t size, char* response) {
     if (size == 0) {
         return -1;
     }
@@ -190,7 +190,7 @@
     return size;
 }
 
-static int64_t _command_send_fd(Transport* transport, const char* cmd, int fd, uint32_t size,
+static int64_t _command_send_fd(Transport* transport, const std::string& cmd, int fd, uint32_t size,
                                 char* response) {
     static constexpr uint32_t MAX_MAP_SIZE = 512 * 1024 * 1024;
     off64_t offset = 0;
@@ -223,15 +223,15 @@
     return size;
 }
 
-static int _command_send_no_data(Transport* transport, const char* cmd, char* response) {
+static int _command_send_no_data(Transport* transport, const std::string& cmd, char* response) {
     return _command_start(transport, cmd, 0, response);
 }
 
-int fb_command(Transport* transport, const char* cmd) {
+int fb_command(Transport* transport, const std::string& cmd) {
     return _command_send_no_data(transport, cmd, 0);
 }
 
-int fb_command_response(Transport* transport, const char* cmd, char* response) {
+int fb_command_response(Transport* transport, const std::string& cmd, char* response) {
     return _command_send_no_data(transport, cmd, response);
 }
 
@@ -339,7 +339,7 @@
     }
 
     std::string cmd(android::base::StringPrintf("download:%08x", size));
-    int r = _command_start(transport, cmd.c_str(), size, 0);
+    int r = _command_start(transport, cmd, size, 0);
     if (r < 0) {
         return -1;
     }
diff --git a/fastboot/util.cpp b/fastboot/util.cpp
index f2bbd34..fb085e7 100644
--- a/fastboot/util.cpp
+++ b/fastboot/util.cpp
@@ -35,35 +35,24 @@
 
 #include "fastboot.h"
 
-double now()
-{
+double now() {
     struct timeval tv;
     gettimeofday(&tv, NULL);
     return (double)tv.tv_sec + (double)tv.tv_usec / 1000000;
 }
 
-char *mkmsg(const char *fmt, ...)
-{
-    char buf[256];
-    char *s;
-    va_list ap;
-
-    va_start(ap, fmt);
-    vsprintf(buf, fmt, ap);
-    va_end(ap);
-
-    s = strdup(buf);
-    if (s == 0) die("out of memory");
-    return s;
-}
-
-void die(const char *fmt, ...)
-{
+void die(const char* fmt, ...) {
     va_list ap;
     va_start(ap, fmt);
     fprintf(stderr,"error: ");
     vfprintf(stderr, fmt, ap);
     fprintf(stderr,"\n");
     va_end(ap);
-    exit(1);
+    exit(EXIT_FAILURE);
+}
+
+char* xstrdup(const char* s) {
+    char* result = strdup(s);
+    if (!result) die("out of memory");
+    return result;
 }