[dbg_unix] Make sure to use execinfo.h only when available, fixes #1

lonetix/sys/dbg_unix.c

@@ -18,8 +18,12 @@
 #include <string.h>
 #include <unistd.h>
 
-#ifdef __GNUC__
+#ifdef __has_include
+#if __has_include(<execinfo.h>)
 #include <execinfo.h>
+
+#define EXECINFO_AVAILABLE 1
+#endif
 #endif
 
 Boolean Sys_IsDebuggerPresent(void)
@@ -63,7 +67,7 @@ size_t Sys_GetBacktrace(void **dest, size_t n)
 	USED(dest);
 	USED(n);
 
-#ifdef __GNUC__
+#ifdef EXECINFO_AVAILABLE
 	if (n > (size_t) (INT_MAX - 1))
 		n = INT_MAX - 1;
 
@@ -84,7 +88,7 @@ size_t Sys_GetBacktrace(void **dest, size_t n)
 
 void *Sys_GetCaller(void)
 {
-#ifdef __GNUC__
+#ifdef EXECINFO_AVAILABLE
 	void *trace[3];  // ourselves, caller, caller's caller
 
 	int n = backtrace(trace, ARRAY_SIZE(trace));
@@ -100,7 +104,7 @@ char *Sys_GetSymbolName(void *sym)
 {
 	USED(sym);
 
-#ifdef __GNUC__
+#ifdef EXECINFO_AVAILABLE
 	static THREAD_LOCAL char buf[128];
 
 	char **names = backtrace_symbols(&sym, 1);
@@ -132,7 +136,7 @@ void Sys_DumpBacktrace(ConHn hn, void **trace, size_t n)
 	USED(trace);
 	USED(n);
 
-#ifdef __GNUC__
+#ifdef EXECINFO_AVAILABLE
 	backtrace_symbols_fd(trace, MIN(n, (size_t) INT_MAX), hn);
 #endif
 }