[sanitizer_common][test] Handle missing REG_STARTEND in Posix/regex_startend.cpp

[ro]

Summary

As reported in D96348, the Posix/regex_startend.cpp test FAILs on Solaris because
REG_STARTEND isn't defined. It's a BSD extension not present everywhere. E.g. AIX doesn't have it, too.

Fixed by wrapping the test in #ifdef REG_STARTEND.

Tested on amd64-pc-solaris2.11, sparcv9-sun-solaris2.11, and x86_64-pc-linux-gnu.

[arichardson]

Thanks, this looks good to me, but maybe wait until one of the sanitizer maintainers has had a look before committing.

compiler-rt/test/sanitizer_common/TestCases/Posix/regex_startend.cpp

 // RUN: %clangxx -O0 -g %s -o %t && %run %t
 /// Check that REG_STARTEND is handled correctly.
 /// This is a regression test for https://github.com/google/sanitizers/issues/1371
 /// Previously, on GLibc systems, the interceptor was calling __compat_regexec
 /// (regexec@GLIBC_2.2.5) insead of the newer __regexec (regexec@GLIBC_2.3.4).
 /// The __compat_regexec strips the REG_STARTEND flag but does not report an error
 /// if other flags are present. This can result in infinite loops for programs that
 /// use REG_STARTEND to find all matches inside a buffer (since ignoring REG_STARTEND
 /// means that the search always starts from the first character).
 
 #include <assert.h>
 #include <regex.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+/// REG_STARTEND is a BSD extension not supported everywhere.
+#ifdef REG_STARTEND
 void test_matched(const regex_t *preg, const char *string, size_t start,
                   size_t end, const char *expected) {
   regmatch_t match[1];
   match[0].rm_so = start;
   match[0].rm_eo = end;
   int rv = regexec(preg, string, 1, match, REG_STARTEND);
   int matchlen = (int)(match[0].rm_eo - match[0].rm_so);
   const char *matchstart = string + match[0].rm_so;
int main(void) {
   test_matched(&regex, "ABCD", 1, 2, nullptr); // Not long enough
   test_matched(&regex, "ABCD", 2, 4, "CD");
   test_matched(&regex, "ABCD", 2, 3, nullptr); // Not long enough
   test_matched(&regex, "ABCD", 3, 4, nullptr); // Not long enough
   regfree(&regex);
   printf("Successful test\n");
   return 0;
 }
+#else
+int main(void) {
+  return 0;
+}
+#endif