1 files changed, 31 insertions, 13 deletions
diff --git a/utils/google-benchmark/src/re.h b/utils/google-benchmark/src/re.h
index 01e9736505e55..fbe25037b4638 100644
--- a/utils/google-benchmark/src/re.h
+++ b/utils/google-benchmark/src/re.h
@@ -17,22 +17,39 @@
 
 #include "internal_macros.h"
 
+// clang-format off
+
+#if !defined(HAVE_STD_REGEX) && \
+    !defined(HAVE_GNU_POSIX_REGEX) && \
+    !defined(HAVE_POSIX_REGEX)
+  // No explicit regex selection; detect based on builtin hints.
+  #if defined(BENCHMARK_OS_LINUX) || defined(BENCHMARK_OS_APPLE)
+    #define HAVE_POSIX_REGEX 1
+  #elif __cplusplus >= 199711L
+    #define HAVE_STD_REGEX 1
+  #endif
+#endif
+
 // Prefer C regex libraries when compiling w/o exceptions so that we can
 // correctly report errors.
-#if defined(BENCHMARK_HAS_NO_EXCEPTIONS) && defined(HAVE_STD_REGEX) && \
+#if defined(BENCHMARK_HAS_NO_EXCEPTIONS) && \
+    defined(BENCHMARK_HAVE_STD_REGEX) && \
     (defined(HAVE_GNU_POSIX_REGEX) || defined(HAVE_POSIX_REGEX))
-#undef HAVE_STD_REGEX
+  #undef HAVE_STD_REGEX
 #endif
 
 #if defined(HAVE_STD_REGEX)
-#include <regex>
+  #include <regex>
 #elif defined(HAVE_GNU_POSIX_REGEX)
-#include <gnuregex.h>
+  #include <gnuregex.h>
 #elif defined(HAVE_POSIX_REGEX)
-#include <regex.h>
+  #include <regex.h>
 #else
 #error No regular expression backend was found!
 #endif
+
+// clang-format on
+
 #include <string>
 
 #include "check.h"
@@ -72,20 +89,21 @@ class Regex {
 
 inline bool Regex::Init(const std::string& spec, std::string* error) {
 #ifdef BENCHMARK_HAS_NO_EXCEPTIONS
-  ((void)error); // suppress unused warning
+  ((void)error);  // suppress unused warning
 #else
   try {
 #endif
-    re_ = std::regex(spec, std::regex_constants::extended);
-    init_ = true;
+  re_ = std::regex(spec, std::regex_constants::extended);
+  init_ = true;
 #ifndef BENCHMARK_HAS_NO_EXCEPTIONS
-  } catch (const std::regex_error& e) {
-    if (error) {
-      *error = e.what();
-    }
+}
+catch (const std::regex_error& e) {
+  if (error) {
+    *error = e.what();
   }
+}
 #endif
-  return init_;
+return init_;
 }
 
 inline Regex::~Regex() {}