diff --git a/docs/32-bit-abi.md b/docs/32-bit-abi.md
index 3be6b1a..7a96e2f 100644
--- a/docs/32-bit-abi.md
+++ b/docs/32-bit-abi.md
@@ -109,3 +109,15 @@
 mutexes for tids that don't fit in 16 bits. This typically manifests as
 a hang in `pthread_mutex_lock` if the libc startup code doesn't detect
 this condition and abort.
+
+
+## `getuid()` and friends wrongly set errno for very large results
+
+This doesn't generally affect Android devices, because we don't have any
+uids/gids/pids large enough, but 32-bit Android doesn't take into account
+that functions like getuid() potentially have return values that cover the
+entire 32-bit, and can't fail. This means that the usual "if the result is
+between -1 and -4096, set errno and return -1" code is inappropriate for
+these functions. Since LP32 is unlikely to be still supported long before
+those limits could ever matter, although -- unlike the others in this
+document -- this defect is actually fixable, it doesn't seem worth fixing.
diff --git a/libc/Android.bp b/libc/Android.bp
index 5afed1a..e4bedba 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -20,31 +20,6 @@
     ],
 }
 
-libc_common_src_files = [
-    "bionic/ether_aton.c",
-    "bionic/ether_ntoa.c",
-    "bionic/exit.cpp",
-    "bionic/initgroups.c",
-    "bionic/isatty.c",
-    "bionic/sched_cpualloc.c",
-    "bionic/sched_cpucount.c",
-    "bionic/sysprop_helpers.cpp",
-    "stdio/fmemopen.cpp",
-    "stdio/parsefloat.c",
-    "stdio/refill.c",
-    "stdio/stdio.cpp",
-    "stdio/stdio_ext.cpp",
-    "stdio/vfscanf.cpp",
-    "stdio/vfwscanf.cpp",
-]
-
-// off64_t/time64_t support on LP32.
-// ========================================================
-libc_common_src_files_32 = [
-    "bionic/legacy_32_bit_support.cpp",
-    "bionic/time64.c",
-]
-
 libc_common_flags = [
     "-D_LIBC=1",
     "-D__BIONIC_LP32_USE_STAT64",
@@ -844,9 +819,12 @@
         "bionic/dup.cpp",
         "bionic/environ.cpp",
         "bionic/error.cpp",
+        "bionic/ether_aton.c",
+        "bionic/ether_ntoa.c",
         "bionic/eventfd.cpp",
         "bionic/exec.cpp",
         "bionic/execinfo.cpp",
+        "bionic/exit.cpp",
         "bionic/faccessat.cpp",
         "bionic/fchmod.cpp",
         "bionic/fchmodat.cpp",
@@ -879,8 +857,10 @@
         "bionic/iconv.cpp",
         "bionic/icu_wrappers.cpp",
         "bionic/ifaddrs.cpp",
+        "bionic/initgroups.c",
         "bionic/inotify_init.cpp",
         "bionic/ioctl.cpp",
+        "bionic/isatty.c",
         "bionic/killpg.cpp",
         "bionic/langinfo.cpp",
         "bionic/lchown.cpp",
@@ -951,6 +931,8 @@
         "bionic/rename.cpp",
         "bionic/rmdir.cpp",
         "bionic/scandir.cpp",
+        "bionic/sched_cpualloc.c",
+        "bionic/sched_cpucount.c",
         "bionic/sched_getaffinity.cpp",
         "bionic/sched_getcpu.cpp",
         "bionic/semaphore.cpp",
@@ -988,6 +970,7 @@
         "bionic/sys_time.cpp",
         "bionic/sysinfo.cpp",
         "bionic/syslog.cpp",
+        "bionic/sysprop_helpers.cpp",
         "bionic/system.cpp",
         "bionic/system_property_api.cpp",
         "bionic/system_property_set.cpp",
@@ -1011,6 +994,16 @@
         "bionic/wcwidth.cpp",
         "bionic/wmempcpy.cpp",
 
+        // Forked but not yet cleaned up/rewritten stdio code.
+        // TODO: finish cleanup.
+        "stdio/fmemopen.cpp",
+        "stdio/parsefloat.c",
+        "stdio/refill.c",
+        "stdio/stdio.cpp",
+        "stdio/stdio_ext.cpp",
+        "stdio/vfscanf.cpp",
+        "stdio/vfwscanf.cpp",
+
         // TODO: why isn't this in a static-libc-only module?
         // This contains a weak stub implementation of __find_icu_symbol for wctype.cpp,
         // which will be overridden by the actual one in libc.so.
@@ -1223,10 +1216,16 @@
         },
     },
 
-    // TODO: move to libc/bionic/legacy_32_bit_support.cpp or #if __LP64__ instead.
     multilib: {
         lib32: {
-            srcs: ["bionic/mmap.cpp"],
+            srcs: [
+                // off64_t/time64_t support on LP32.
+                "bionic/legacy_32_bit_support.cpp",
+                "bionic/time64.c",
+
+                // TODO: move to libc/bionic/legacy_32_bit_support.cpp or #if __LP64__ instead.
+                "bionic/mmap.cpp",
+            ],
         },
     },
 
@@ -1336,20 +1335,13 @@
 }
 
 // ========================================================
-// libc_common.a
+// libc_common.a --- everything shared by libc.a and libc.so
 // ========================================================
 
 cc_library_static {
     defaults: ["libc_defaults"],
     name: "libc_common",
 
-    srcs: libc_common_src_files,
-    multilib: {
-        lib32: {
-            srcs: libc_common_src_files_32,
-        },
-    },
-
     whole_static_libs: [
         "libarm-optimized-routines-string",
         "libasync_safe",
@@ -1377,7 +1369,7 @@
 }
 
 // ========================================================
-// libc_static_dispatch.a
+// libc_static_dispatch.a --- libc.a ifuncs
 // ========================================================
 cc_library_static {
     defaults: ["libc_defaults"],
@@ -1403,7 +1395,7 @@
 }
 
 // ========================================================
-// libc_dynamic_dispatch.a
+// libc_dynamic_dispatch.a --- libc.so ifuncs
 // ========================================================
 cc_library_static {
     defaults: ["libc_defaults"],
@@ -1897,6 +1889,7 @@
         "//external/gwp_asan",
         "//external/jemalloc_new",
         "//external/libunwind_llvm",
+        "//external/llvm-libc",
         "//external/scudo",
         "//system/core/property_service/libpropertyinfoparser",
         "//system/extras/toolchain-extras",
diff --git a/libc/private/bsd_sys_param.h b/libc/private/bsd_sys_param.h
index be5f692..ab54aa0 100644
--- a/libc/private/bsd_sys_param.h
+++ b/libc/private/bsd_sys_param.h
@@ -20,4 +20,4 @@
 
 /* OpenBSD has these in <sys/param.h>, but "ALIGN" isn't something we want to reserve. */
 #define ALIGNBYTES (sizeof(uintptr_t) - 1)
-#define ALIGN(p) (((uintptr_t)(p) + ALIGNBYTES) & ~ALIGNBYTES)
+#define ALIGN(p) ((__BIONIC_CAST(reinterpret_cast, uintptr_t, p) + ALIGNBYTES) & ~ALIGNBYTES)
diff --git a/libc/stdio/local.h b/libc/stdio/local.h
index a5eb636..62efea1 100644
--- a/libc/stdio/local.h
+++ b/libc/stdio/local.h
@@ -236,7 +236,7 @@
 /* OpenBSD exposes these in <stdio.h>, but we only want them exposed to the implementation. */
 #define __sferror(p) (((p)->_flags & __SERR) != 0)
 #define __sclearerr(p) ((void)((p)->_flags &= ~(__SERR | __SEOF)))
-#define __sgetc(p) (--(p)->_r < 0 ? __srget(p) : (int)(*(p)->_p++))
+#define __sgetc(p) (--(p)->_r < 0 ? __srget(p) : __BIONIC_CAST(static_cast, int, *(p)->_p++))
 
 /* OpenBSD declares these in fvwrite.h, but we share them with C++ parts of the implementation. */
 struct __siov {
@@ -288,7 +288,7 @@
 char* __hldtoa(long double, const char*, int, int*, int*, char**);
 char* __ldtoa(long double*, int, int, int*, int*, char**);
 
-#define WCIO_GET(fp) (_EXT(fp) ? &(_EXT(fp)->_wcio) : (struct wchar_io_data*)0)
+#define WCIO_GET(fp) (_EXT(fp) ? &(_EXT(fp)->_wcio) : NULL)
 
 #define ORIENT_BYTES (-1)
 #define ORIENT_UNKNOWN 0
diff --git a/libc/stdio/scanf_common.h b/libc/stdio/scanf_common.h
index 8132e90..1b6b87f 100644
--- a/libc/stdio/scanf_common.h
+++ b/libc/stdio/scanf_common.h
@@ -82,7 +82,7 @@
 #define CT_FLOAT 4   // Float: strtod
 
 #define to_digit(c) static_cast<int>((c) - '0')
-#define is_digit(c) ((unsigned)to_digit(c) <= 9)
+#define is_digit(c) (static_cast<unsigned>(to_digit(c)) <= 9)
 
 // Append a digit to a value and check for overflow.
 #define APPEND_DIGIT(val, dig)               \
@@ -112,4 +112,4 @@
   __fortify_fatal("%%w%s%d is unsupported", fast ? "f" : "", size);
 }
 
-#pragma clang diagnostic pop
\ No newline at end of file
+#pragma clang diagnostic pop
diff --git a/libc/stdio/vfscanf.cpp b/libc/stdio/vfscanf.cpp
index 3607995..92ff541 100644
--- a/libc/stdio/vfscanf.cpp
+++ b/libc/stdio/vfscanf.cpp
@@ -629,10 +629,10 @@
          * as `[-+]0`.
          */
         if (flags & NDIGITS) {
-          if (p > buf) (void)ungetc(*(u_char*)--p, fp);
+          if (p > buf) ungetc(*reinterpret_cast<u_char*>(--p), fp);
           goto match_failure;
         }
-        c = ((u_char*)p)[-1];
+        c = reinterpret_cast<u_char*>(p)[-1];
         if ((base == 2 && (c == 'b' || c == 'B')) || c == 'x' || c == 'X') {
           --p;
           (void)ungetc(c, fp);
@@ -647,7 +647,7 @@
             res = strtoimax(buf, nullptr, base);
           }
           if (flags & POINTER) {
-            *va_arg(ap, void**) = (void*)(uintptr_t)res;
+            *va_arg(ap, void**) = reinterpret_cast<void*>(res);
           } else if (flags & MAXINT) {
             *va_arg(ap, intmax_t*) = res;
           } else if (flags & LLONG) {
@@ -685,7 +685,7 @@
             float res = strtof(buf, &p);
             *va_arg(ap, float*) = res;
           }
-          if ((size_t)(p - buf) != width) abort();
+          if (static_cast<size_t>(p - buf) != width) abort();
           nassigned++;
         }
         nread += width;
diff --git a/libc/stdio/vfwscanf.cpp b/libc/stdio/vfwscanf.cpp
index 3df4a87..21d1783 100644
--- a/libc/stdio/vfwscanf.cpp
+++ b/libc/stdio/vfwscanf.cpp
@@ -32,6 +32,7 @@
  */
 
 #include "scanf_common.h"
+
 // An interpretive version of __sccl from vfscanf.c --- a table of all wchar_t values would
 // be a little too expensive, and some kind of compressed version isn't worth the trouble.
 static inline bool in_ccl(wchar_t wc, const wchar_t* ccl) {
@@ -335,7 +336,7 @@
           if (!(flags & SUPPRESS)) p = va_arg(ap, wchar_t*);
           n = 0;
           while (width-- != 0 && (wi = __fgetwc_unlock(fp)) != WEOF) {
-            if (!(flags & SUPPRESS)) *p++ = (wchar_t)wi;
+            if (!(flags & SUPPRESS)) *p++ = static_cast<wchar_t>(wi);
             n++;
           }
           if (n == 0) goto input_failure;
@@ -348,10 +349,10 @@
           while (width != 0 && (wi = __fgetwc_unlock(fp)) != WEOF) {
             if (width >= MB_CUR_MAX && !(flags & SUPPRESS)) {
               nconv = wcrtomb(mbp, wi, &mbs);
-              if (nconv == (size_t)-1) goto input_failure;
+              if (nconv == static_cast<size_t>(-1)) goto input_failure;
             } else {
               nconv = wcrtomb(mbbuf, wi, &mbs);
-              if (nconv == (size_t)-1) goto input_failure;
+              if (nconv == static_cast<size_t>(-1)) goto input_failure;
               if (nconv > width) {
                 __ungetwc(wi, fp);
                 break;
@@ -373,7 +374,7 @@
       case CT_STRING:
         // CT_CCL: scan a (nonempty) character class (sets NOSKIP).
         // CT_STRING: like CCL, but zero-length string OK, & no NOSKIP.
-        if (width == 0) width = (size_t)~0; // 'infinity'.
+        if (width == 0) width = SIZE_MAX; // 'infinity'.
         if ((flags & SUPPRESS) && (flags & LONG)) {
           n = 0;
           while ((wi = __fgetwc_unlock(fp)) != WEOF && width-- != 0 && ((c == CT_CCL && in_ccl(wi, ccl)) || (c == CT_STRING && !iswspace(wi)))) n++;
@@ -381,7 +382,7 @@
         } else if (flags & LONG) {
           p0 = p = va_arg(ap, wchar_t*);
           while ((wi = __fgetwc_unlock(fp)) != WEOF && width-- != 0 && ((c == CT_CCL && in_ccl(wi, ccl)) || (c == CT_STRING && !iswspace(wi)))) {
-            *p++ = (wchar_t)wi;
+            *p++ = static_cast<wchar_t>(wi);
           }
           if (wi != WEOF) __ungetwc(wi, fp);
           n = p - p0;
@@ -392,10 +393,10 @@
           while ((wi = __fgetwc_unlock(fp)) != WEOF && width != 0 && ((c == CT_CCL && in_ccl(wi, ccl)) || (c == CT_STRING && !iswspace(wi)))) {
             if (width >= MB_CUR_MAX && !(flags & SUPPRESS)) {
               nconv = wcrtomb(mbp, wi, &mbs);
-              if (nconv == (size_t)-1) goto input_failure;
+              if (nconv == static_cast<size_t>(-1)) goto input_failure;
             } else {
               nconv = wcrtomb(mbbuf, wi, &mbs);
-              if (nconv == (size_t)-1) goto input_failure;
+              if (nconv == static_cast<size_t>(-1)) goto input_failure;
               if (nconv > width) break;
               if (!(flags & SUPPRESS)) memcpy(mbp, mbbuf, nconv);
             }
@@ -485,7 +486,7 @@
             case 'e':
             case 'f':
               if (base == 0) base = 10;
-              if (base != 16 && (int)(c - '0') >= base) break; /* not legal here */
+              if (base != 16 && static_cast<int>(c - '0') >= base) break; /* not legal here */
               flags &= ~(SIGNOK | PFBOK | PFXOK | NDIGITS);
               goto ok;
 
@@ -523,7 +524,7 @@
           /*
            * c is legal: store it and look at the next.
            */
-          *p++ = (wchar_t)c;
+          *p++ = static_cast<wchar_t>(c);
         }
         /*
          * If we had only a sign, it is no good; push back the sign.
@@ -548,7 +549,7 @@
           else
             res = wcstoumax(buf, NULL, base);
           if (flags & POINTER)
-            *va_arg(ap, void**) = (void*)(uintptr_t)res;
+            *va_arg(ap, void**) = reinterpret_cast<void*>(res);
           else if (flags & MAXINT)
             *va_arg(ap, intmax_t*) = res;
           else if (flags & LLONG)
@@ -587,7 +588,7 @@
             float res = wcstof(buf, &p);
             *va_arg(ap, float*) = res;
           }
-          if (p - buf != (ptrdiff_t)width) abort();
+          if (static_cast<size_t>(p - buf) != width) abort();
           nassigned++;
         }
         nread += width;