Fix incompatible strerror_r for non-gnu/windows libc (#493)

Signed-off-by: Russell McGuire <russell.w.mcguire@intel.com>

Author: rwmcguir

source/utils/ze_logger.cpp

@@ -105,20 +105,41 @@ const char *levelColor(LogLevel l) {
 }
 
 // Thread-safe, portable errno-to-string conversion.
-// MSVC deprecates strerror() in favour of strerror_s(); POSIX provides strerror_r().
+// strerror_r has two incompatible POSIX signatures depending on libc:
+//   - GNU:  char *strerror_r(int, char *, size_t)   (glibc with _GNU_SOURCE)
+//   - XSI:  int   strerror_r(int, char *, size_t)   (musl, Bionic, uClibc, POSIX)
+// _GNU_SOURCE is not a reliable discriminator — it requests GNU extensions but
+// only glibc honours it for strerror_r.  We let overload resolution pick the
+// right handler based on the actual return type the compiler sees, so the
+// code is correct under any libc without preprocessor guesswork.
+// MSVC uses strerror_s.
+#ifndef _WIN32
+// Mark both overloads as "may be unused" — only one matches strerror_r's
+// signature for any given libc, so the other is intentionally dead code.
+#if defined(__GNUC__) || defined(__clang__)
+#define ZE_LOGGER_MAYBE_UNUSED __attribute__((unused))
+#else
+#define ZE_LOGGER_MAYBE_UNUSED
+#endif
+// XSI variant: returns int (0 on success); message is in `buf`.
+static ZE_LOGGER_MAYBE_UNUSED std::string strerrorRDispatch(int /*ret*/, char *buf) {
+    return std::string(buf);
+}
+// GNU variant: returns char* that may or may not point at `buf`.
+static ZE_LOGGER_MAYBE_UNUSED std::string strerrorRDispatch(char *ret, char *buf) {
+    return ret ? std::string(ret) : std::string(buf);
+}
+#undef ZE_LOGGER_MAYBE_UNUSED
+#endif
+
 static std::string errnoToString(int err) {
     char buf[256];
+    buf[0] = '\0';
 #ifdef _WIN32
     strerror_s(buf, sizeof(buf), err);
     return buf;
-#elif defined(_GNU_SOURCE)
-    // GNU strerror_r returns char* (may or may not use buf)
-    const char *result = strerror_r(err, buf, sizeof(buf));
-    return result ? result : buf;
 #else
-    // XSI-compliant strerror_r returns int
-    strerror_r(err, buf, sizeof(buf));
-    return buf;
+    return strerrorRDispatch(strerror_r(err, buf, sizeof(buf)), buf);
 #endif
 }