Change std::regex detection test to detect bug in libstdc++.

libstdc++'s std::regex has (or had) a bug in std::regex::operator=(...) that caused undefined behaviour. Clang will detect this and compile the function so that it crashes at runtime. This patch tried to detect that bug during configuration.

Change std::regex detection test to detect bug in libstdc++.
c5a362b4 · Eric Fiselier · 056a008a · c5a362b4
Commit c5a362b4 authored Mar 06, 2015 by Eric Fiselier
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std_regex.cpp cmake/std_regex.cpp +3 -3

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--- a/cmake/std_regex.cpp
+++ b/cmake/std_regex.cpp
@@ -2,9 +2,9 @@
 #include <string>
 int main() {
  const std::string str = "test0159";
-  const std::regex re(
+  std::regex re;
-      "^[a-z]+[0-9]+$",
+  re = std::regex("^[a-z]+[0-9]+$",
-      std::regex_constants::extended | std::regex_constants::nosubs);
+       std::regex_constants::extended | std::regex_constants::nosubs);
  return std::regex_search(str, re) ? 0 : -1;
 }