diff --git a/libc/include/bits/fortify/poll.h b/libc/include/bits/fortify/poll.h
index 718ee96..0d9b927 100644
--- a/libc/include/bits/fortify/poll.h
+++ b/libc/include/bits/fortify/poll.h
@@ -40,8 +40,7 @@
 __BIONIC_FORTIFY_INLINE
 int poll(struct pollfd* const fds __pass_object_size, nfds_t fd_count, int timeout)
     __overloadable
-    __clang_error_if(__bos(fds) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                       __bos(fds) < sizeof(*fds) * fd_count,
+    __clang_error_if(__bos_unevaluated_lt(__bos(fds), sizeof(*fds) * fd_count),
                      "in call to 'poll', fd_count is larger than the given buffer") {
   size_t bos_fds = __bos(fds);
 
@@ -54,8 +53,7 @@
 __BIONIC_FORTIFY_INLINE
 int ppoll(struct pollfd* const fds __pass_object_size, nfds_t fd_count, const struct timespec* timeout, const sigset_t* mask)
     __overloadable
-    __clang_error_if(__bos(fds) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                       __bos(fds) < sizeof(*fds) * fd_count,
+    __clang_error_if(__bos_unevaluated_lt(__bos(fds), sizeof(*fds) * fd_count),
                      "in call to 'ppoll', fd_count is larger than the given buffer") {
   size_t bos_fds = __bos(fds);
 
@@ -69,8 +67,7 @@
 __BIONIC_FORTIFY_INLINE
 int ppoll64(struct pollfd* const fds __pass_object_size, nfds_t fd_count, const struct timespec* timeout, const sigset64_t* mask)
     __overloadable
-    __clang_error_if(__bos(fds) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                       __bos(fds) < sizeof(*fds) * fd_count,
+    __clang_error_if(__bos_unevaluated_lt(__bos(fds), sizeof(*fds) * fd_count),
                      "in call to 'ppoll64', fd_count is larger than the given buffer") {
   size_t bos_fds = __bos(fds);
 
diff --git a/libc/include/bits/fortify/socket.h b/libc/include/bits/fortify/socket.h
index 3d070c5..c1a85c6 100644
--- a/libc/include/bits/fortify/socket.h
+++ b/libc/include/bits/fortify/socket.h
@@ -44,8 +44,7 @@
 __BIONIC_FORTIFY_INLINE
 ssize_t recvfrom(int fd, void* const buf __pass_object_size0, size_t len, int flags, struct sockaddr* src_addr, socklen_t* addr_len)
     __overloadable
-    __clang_error_if(__bos(buf) != __BIONIC_FORTIFY_UNKNOWN_SIZE && __bos(buf) < len,
-                     __recvfrom_bad_size) {
+    __clang_error_if(__bos_unevaluated_lt(__bos0(buf), len), __recvfrom_bad_size) {
   size_t bos = __bos0(buf);
 
   if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
@@ -59,8 +58,7 @@
 __BIONIC_FORTIFY_INLINE
 ssize_t sendto(int fd, const void* const buf __pass_object_size0, size_t len, int flags, const struct sockaddr* dest_addr, socklen_t addr_len)
     __overloadable
-    __clang_error_if(__bos0(buf) != __BIONIC_FORTIFY_UNKNOWN_SIZE && __bos0(buf) < len,
-                     __sendto_bad_size) {
+    __clang_error_if(__bos_unevaluated_lt(__bos0(buf), len), __sendto_bad_size) {
   size_t bos = __bos0(buf);
 
   if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
@@ -73,7 +71,7 @@
 __BIONIC_FORTIFY_INLINE
 ssize_t recv(int socket, void* const buf __pass_object_size0, size_t len, int flags)
     __overloadable
-    __clang_error_if(__bos0(buf) != __BIONIC_FORTIFY_UNKNOWN_SIZE && __bos0(buf) < len,
+    __clang_error_if(__bos_unevaluated_lt(__bos0(buf), len),
                      "'recv' called with size bigger than buffer") {
   return recvfrom(socket, buf, len, flags, NULL, 0);
 }
@@ -81,7 +79,7 @@
 __BIONIC_FORTIFY_INLINE
 ssize_t send(int socket, const void* const buf __pass_object_size0, size_t len, int flags)
     __overloadable
-    __clang_error_if(__bos0(buf) != __BIONIC_FORTIFY_UNKNOWN_SIZE && __bos0(buf) < len,
+    __clang_error_if(__bos_unevaluated_lt(__bos0(buf), len),
                      "'send' called with size bigger than buffer") {
   return sendto(socket, buf, len, flags, NULL, 0);
 }
diff --git a/libc/include/bits/fortify/stdio.h b/libc/include/bits/fortify/stdio.h
index 0b5700a..fc7d359 100644
--- a/libc/include/bits/fortify/stdio.h
+++ b/libc/include/bits/fortify/stdio.h
@@ -57,8 +57,7 @@
 __BIONIC_ERROR_FUNCTION_VISIBILITY
 int snprintf(char* dest, size_t size, const char* format)
     __overloadable
-    __enable_if(__bos(dest) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                    __bos(dest) < __builtin_strlen(format),
+    __enable_if(__bos_unevaluated_lt(__bos(dest), __builtin_strlen(format)),
                 "format string will always overflow destination buffer")
     __errorattr("format string will always overflow destination buffer");
 
@@ -75,8 +74,7 @@
 __BIONIC_ERROR_FUNCTION_VISIBILITY
 int sprintf(char* dest, const char* format)
     __overloadable
-    __enable_if(__bos(dest) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                __bos(dest) < __builtin_strlen(format),
+    __enable_if(__bos_unevaluated_lt(__bos(dest), __builtin_strlen(format)),
                 "format string will always overflow destination buffer")
     __errorattr("format string will always overflow destination buffer");
 
@@ -96,7 +94,7 @@
         __overloadable
         __clang_error_if(__unsafe_check_mul_overflow(size, count),
                          "in call to 'fread', size * count overflows")
-        __clang_error_if(__bos(buf) != __BIONIC_FORTIFY_UNKNOWN_SIZE && size * count > __bos(buf),
+        __clang_error_if(__bos_unevaluated_lt(__bos0(buf), size * count),
                          "in call to 'fread', size * count is too large for the given buffer") {
     size_t bos = __bos0(buf);
 
@@ -111,7 +109,7 @@
         __overloadable
         __clang_error_if(__unsafe_check_mul_overflow(size, count),
                          "in call to 'fwrite', size * count overflows")
-        __clang_error_if(__bos(buf) != __BIONIC_FORTIFY_UNKNOWN_SIZE && size * count > __bos(buf),
+        __clang_error_if(__bos_unevaluated_lt(__bos0(buf), size * count),
                          "in call to 'fwrite', size * count is too large for the given buffer") {
     size_t bos = __bos0(buf);
 
@@ -128,7 +126,7 @@
 char* fgets(char* const __pass_object_size dest, int size, FILE* stream)
         __overloadable
         __clang_error_if(size < 0, "in call to 'fgets', size should not be negative")
-        __clang_error_if(size > __bos(dest),
+        __clang_error_if(__bos_unevaluated_lt(__bos(dest), size),
                          "in call to 'fgets', size is larger than the destination buffer") {
     size_t bos = __bos(dest);
 
diff --git a/libc/include/bits/fortify/stdlib.h b/libc/include/bits/fortify/stdlib.h
index d47c0b0..eff909f 100644
--- a/libc/include/bits/fortify/stdlib.h
+++ b/libc/include/bits/fortify/stdlib.h
@@ -38,8 +38,8 @@
 #define __PATH_MAX 4096
 
 char* realpath(const char* path, char* resolved)
-        __clang_error_if(__bos(resolved) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                         __bos(resolved) < __PATH_MAX, __realpath_buf_too_small_str)
+        __clang_error_if(__bos_unevaluated_lt(__bos(resolved), __PATH_MAX),
+                         __realpath_buf_too_small_str)
         __clang_error_if(!path, "'realpath': NULL path is never correct; flipped arguments?");
 /* No need for a definition; the only issues we can catch are at compile-time. */
 
diff --git a/libc/include/bits/fortify/string.h b/libc/include/bits/fortify/string.h
index 14bb133..80eb43e 100644
--- a/libc/include/bits/fortify/string.h
+++ b/libc/include/bits/fortify/string.h
@@ -44,7 +44,7 @@
 __BIONIC_FORTIFY_INLINE
 void* memcpy(void* const dst __pass_object_size0, const void* src, size_t copy_amount)
         __overloadable
-        __clang_error_if(__bos0(dst) != __BIONIC_FORTIFY_UNKNOWN_SIZE && __bos0(dst) < copy_amount,
+        __clang_error_if(__bos_unevaluated_lt(__bos0(dst), copy_amount),
                          "'memcpy' called with size bigger than buffer") {
     return __builtin___memcpy_chk(dst, src, copy_amount, __bos0(dst));
 }
@@ -52,7 +52,7 @@
 __BIONIC_FORTIFY_INLINE
 void* memmove(void* const dst __pass_object_size0, const void* src, size_t len)
         __overloadable
-        __clang_error_if(__bos0(dst) != __BIONIC_FORTIFY_UNKNOWN_SIZE && __bos0(dst) < len,
+        __clang_error_if(__bos_unevaluated_lt(__bos0(dst), len),
                          "'memmove' called with size bigger than buffer") {
     return __builtin___memmove_chk(dst, src, len, __bos0(dst));
 }
@@ -62,8 +62,7 @@
 __BIONIC_FORTIFY_INLINE
 char* stpcpy(char* const dst __pass_object_size, const char* src)
         __overloadable
-        __clang_error_if(__bos(dst) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                             __bos(dst) <= __builtin_strlen(src),
+        __clang_error_if(__bos_unevaluated_leq(__bos(dst), __builtin_strlen(src)),
                          "'stpcpy' called with string bigger than buffer") {
     return __builtin___stpcpy_chk(dst, src, __bos(dst));
 }
@@ -73,8 +72,7 @@
 __BIONIC_FORTIFY_INLINE
 char* strcpy(char* const dst __pass_object_size, const char* src)
         __overloadable
-        __clang_error_if(__bos(dst) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
-                             __bos(dst) <= __builtin_strlen(src),
+        __clang_error_if(__bos_unevaluated_leq(__bos(dst), __builtin_strlen(src)),
                          "'strcpy' called with string bigger than buffer") {
     return __builtin___strcpy_chk(dst, src, __bos(dst));
 }
@@ -92,7 +90,7 @@
 __BIONIC_FORTIFY_INLINE
 void* memset(void* const s __pass_object_size0, int c, size_t n)
         __overloadable
-        __clang_error_if(__bos0(s) != __BIONIC_FORTIFY_UNKNOWN_SIZE && __bos0(s) < n,
+        __clang_error_if(__bos_unevaluated_lt(__bos0(s), n),
                          "'memset' called with size bigger than buffer")
         /* If you're a user who wants this warning to go away: use `(&memset)(foo, bar, baz)`. */
         __clang_warning_if(c && !n, "'memset' will set 0 bytes; maybe the arguments got flipped?") {
diff --git a/libc/include/bits/fortify/unistd.h b/libc/include/bits/fortify/unistd.h
index a07907b..04c7495 100644
--- a/libc/include/bits/fortify/unistd.h
+++ b/libc/include/bits/fortify/unistd.h
@@ -63,7 +63,7 @@
     __clang_error_if((what) > SSIZE_MAX, "in call to '" #fn "', '" #what "' must be <= SSIZE_MAX")
 
 #define __error_if_overflows_objectsize(what, objsize, fn) \
-    __clang_error_if((objsize) != __BIONIC_FORTIFY_UNKNOWN_SIZE && (what) > (objsize), \
+    __clang_error_if(__bos_unevaluated_lt((objsize), (what)), \
                      "in call to '" #fn "', '" #what "' bytes overflows the given object")
 
 #if __ANDROID_API__ >= __ANDROID_API_N__
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index ca9374e..f36b78e 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -289,6 +289,14 @@
 #define __pass_object_size __pass_object_size_n(__bos_level)
 #define __pass_object_size0 __pass_object_size_n(0)
 
+/* Intended for use in unevaluated contexts, e.g. diagnose_if conditions. */
+#define __bos_unevaluated_lt(bos_val, val) \
+  ((bos_val) != __BIONIC_FORTIFY_UNKNOWN_SIZE && (bos_val) < (val))
+
+#define __bos_unevaluated_leq(bos_val, val) \
+  ((bos_val) != __BIONIC_FORTIFY_UNKNOWN_SIZE && (bos_val) <= (val))
+
+
 #if defined(__BIONIC_FORTIFY) || defined(__BIONIC_DECLARE_FORTIFY_HELPERS)
 #  define __BIONIC_INCLUDE_FORTIFY_HEADERS 1
 #endif