[CoreFoundation][Build] Explicitly check for a few functions.

Use CMake to check for the existence of strlcpy(), strlcat() and
issetugid() before using them.

rdar://123381867

Author: al45tair

CoreFoundation/Base.subproj/CoreFoundation_Prefix.h

@@ -189,7 +189,8 @@ static dispatch_queue_t __ ## PREFIX ## Queue(void) {			\
 #define CF_RETAIN_BALANCED_ELSEWHERE(obj, identified_location) do { } while (0)
 #endif
 
-#if (TARGET_OS_LINUX && !TARGET_OS_ANDROID && !TARGET_OS_CYGWIN) || TARGET_OS_WIN32
+#if !TARGET_OS_MAC
+#if !HAVE_STRLCPY
 CF_INLINE size_t
 strlcpy(char * dst, const char * src, size_t maxlen) {
     const size_t srclen = strlen(src);
@@ -201,7 +202,9 @@ strlcpy(char * dst, const char * src, size_t maxlen) {
     }
     return srclen;
 }
+#endif
 
+#if !HAVE_STRLCAT
 CF_INLINE size_t
 strlcat(char * dst, const char * src, size_t maxlen) {
     const size_t srclen = strlen(src);
@@ -216,6 +219,7 @@ strlcat(char * dst, const char * src, size_t maxlen) {
     return dstlen + srclen;
 }
 #endif
+#endif // !TARGET_OS_MAC
 
 #if TARGET_OS_WIN32
 // Compatibility with boolean.h
@@ -300,7 +304,7 @@ typedef unsigned long fd_mask;
 #endif
 
 
-#if !TARGET_OS_CYGWIN && !TARGET_OS_BSD
+#if !TARGET_OS_MAC && !HAVE_ISSETUGID
 #define issetugid() 0
 #endif
 

CoreFoundation/CMakeLists.txt

@@ -90,6 +90,21 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL Windows)
   endif()
 endif()
 
+# Look for some functions that may not be present on all platforms
+check_symbol_exists(strlcpy "string.h" HAVE_STRLCPY)
+check_symbol_exists(strlcat "string.h" HAVE_STRLCAT)
+check_symbol_exists(issetugid "unistd.h" HAVE_ISSETUGID)
+
+if(HAVE_STRLCPY)
+  add_compile_definitions($<$<COMPILE_LANGUAGE:C>:HAVE_STRLCPY>)
+endif()
+if(HAVE_STRLCAT)
+  add_compile_definitions($<$<COMPILE_LANGUAGE:C>:HAVE_STRLCAT>)
+endif()
+if(HAVE_ISSETUGID)
+  add_compile_definitions($<$<COMPILE_LANGUAGE:C>:HAVE_ISSETUGID>)
+endif()
+
 add_compile_definitions($<$<COMPILE_LANGUAGE:C>:U_SHOW_DRAFT_API>)
 add_compile_definitions($<$<COMPILE_LANGUAGE:C>:CF_BUILDING_CF>)