Detect accept4 in configure/CMake. Enable accept4 for musl. Musl has no dedicated macro so it is detected as non glibc/bionic/uclibc on Linux/Android.

.wolfssl_known_macro_extras

@@ -1388,6 +1388,7 @@ __TMS320C55X__
 __TURBOC__
 __UCLIBC_LINUX_SPECIFIC__
 __UCLIBC_MAJOR__
+__UCLIBC__
 __UNIX__
 __USE_GNU
 __USE_MISC

CMakeLists.txt

@@ -145,6 +145,7 @@ check_function_exists("socket" HAVE_SOCKET)
 check_function_exists("strftime" HAVE_STRFTIME)
 check_function_exists("__atomic_fetch_add" HAVE_C___ATOMIC)
 check_function_exists("getpid" HAVE_GETPID)
+check_function_exists("accept4" HAVE_ACCEPT4)
 
 include(CheckSymbolExists)
 check_symbol_exists(isascii "ctype.h" HAVE_ISASCII)

cmake/config.in

@@ -13,6 +13,9 @@
 /* Define to 1 if you have the <errno.h> header file. */
 #cmakedefine HAVE_ERRNO_H @HAVE_ERRNO_H@
 
+/* Define to 1 if you have the `accept4' function. */
+#cmakedefine HAVE_ACCEPT4 @HAVE_ACCEPT4@
+
 /* Define to 1 if you have the `getaddrinfo' function. */
 #cmakedefine HAVE_GETADDRINFO @HAVE_GETADDRINFO@
 

configure.ac

@@ -288,6 +288,9 @@ fi
     #include <sys/random.h>
 #endif
 ]])
+# accept4() is declared under _GNU_SOURCE, which wc_port.c defines itself, so
+# linkability alone is decisive.
+AC_CHECK_FUNCS([accept4])
 
 AC_PROG_INSTALL
 AC_TYPE_SIZE_T

tests/unit-mcdc/test_wc_port_whitebox.c

@@ -42,10 +42,8 @@
  * technique mcdc_fault_hash.h uses for the hash primitives. Ordering is
  * load-bearing and mirrors that header exactly:
  *   1. define _GNU_SOURCE before the first libc header, exactly as
- *      wc_port.c does at its own top. Without it glibc does not declare
- *      accept4(), __USE_GNU is never set, wc_port.c's WC_HAVE_ACCEPT4 stays
- *      undefined, and the block that CONTAINS the target guard would
- *      compile out of this TU entirely;
+ *      wc_port.c does at its own top, so that glibc declares accept4() for
+ *      the wrapper below;
  *   2. include <sys/socket.h> so the REAL accept4() declaration is in scope
  *      and is never rewritten by the macro;
  *   3. define the wrapper, which is compiled BEFORE the macro exists and so
@@ -63,6 +61,11 @@
     #define _GNU_SOURCE 1
 #endif
 
+/* HAVE_ACCEPT4 for the gate below comes from config.h, as in wc_port.c. */
+#ifdef HAVE_CONFIG_H
+    #include <config.h>
+#endif
+
 #if (defined(__unix__) || defined(__APPLE__)) && \
     !defined(WOLFSSL_LINUXKM) && !defined(WOLFSSL_KERNEL_MODE) && \
     !defined(WOLFSSL_ZEPHYR) && !defined(WOLFSSL_SGX)
@@ -71,13 +74,23 @@
 #endif
 
 /* The Linux half of wc_port.c's WC_HAVE_ACCEPT4 test; keep them identical. */
-#if (defined(__linux__) || defined(__ANDROID__)) && defined(__USE_GNU) && \
-    ((defined(__GLIBC__) && \
-      (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 10))) || \
-     (defined(__UCLIBC_LINUX_SPECIFIC__) && (__UCLIBC_MAJOR__ >= 1)) || \
-     (defined(__ANDROID_API__) && (__ANDROID_API__ >= 21)))
-#define WB_HAVE_ACCEPT4_HOOK
+#if defined(__linux__) || defined(__ANDROID__)
+    #ifdef HAVE_CONFIG_H
+        #ifdef HAVE_ACCEPT4
+            #define WB_HAVE_ACCEPT4_HOOK
+        #endif
+    #elif (defined(__USE_GNU) && \
+           ((defined(__GLIBC__) && \
+             (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 10))) || \
+            (defined(__UCLIBC_LINUX_SPECIFIC__) && (__UCLIBC_MAJOR__ >= 1)) || \
+            (defined(__ANDROID_API__) && (__ANDROID_API__ >= 21)))) || \
+          (!defined(__GLIBC__) && !defined(__UCLIBC__) && \
+           !defined(__ANDROID__))
+        #define WB_HAVE_ACCEPT4_HOOK
+    #endif
+#endif
 
+#ifdef WB_HAVE_ACCEPT4_HOOK
 /* 0 = pass through to the real accept4(); otherwise fail with this errno. */
 static int wb_accept4_errno = 0;
 

wolfcrypt/src/wc_port.c

@@ -5752,13 +5752,24 @@ char* wolfSSL_strnstr(const char* s1, const char* s2, size_t n)
     #define SOCK_CLOEXEC 0
 #endif
 
-/* accept4(): glibc 2.10, uClibc-ng, bionic API 21, FreeBSD 10. */
-#if (defined(__linux__) || defined(__ANDROID__)) && defined(__USE_GNU) && \
-    ((defined(__GLIBC__) && \
-      (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 10))) || \
-     (defined(__UCLIBC_LINUX_SPECIFIC__) && (__UCLIBC_MAJOR__ >= 1)) || \
-     (defined(__ANDROID_API__) && (__ANDROID_API__ >= 21)))
-    #define WC_HAVE_ACCEPT4
+/* accept4(): the configure/CMake probe (HAVE_ACCEPT4) decides when config.h
+ * is in use; otherwise glibc 2.10, uClibc-ng, bionic API 21, and musl, which
+ * has no identifying macro (Linux that is neither glibc, uClibc nor bionic).
+ * FreeBSD 10. */
+#if defined(__linux__) || defined(__ANDROID__)
+    #ifdef HAVE_CONFIG_H
+        #ifdef HAVE_ACCEPT4
+            #define WC_HAVE_ACCEPT4
+        #endif
+    #elif (defined(__USE_GNU) && \
+           ((defined(__GLIBC__) && \
+             (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 10))) || \
+            (defined(__UCLIBC_LINUX_SPECIFIC__) && (__UCLIBC_MAJOR__ >= 1)) || \
+            (defined(__ANDROID_API__) && (__ANDROID_API__ >= 21)))) || \
+          (!defined(__GLIBC__) && !defined(__UCLIBC__) && \
+           !defined(__ANDROID__))
+        #define WC_HAVE_ACCEPT4
+    #endif
 #elif defined(__FreeBSD__) && defined(__BSD_VISIBLE) && __BSD_VISIBLE && \
     (__FreeBSD_version >= 1000000)
     #define WC_HAVE_ACCEPT4