Use LLVM-style include guard in regex_impl.h

[hans]

Summary

The previous include guard (_REGEX_H_) is also used in a macOS SDK header (xlocale.h), causing potential for trouble. This was previously addressed in 2b8b90a7686858b1d22cae6fcfbd0904135112aa, but renaming the macro in line with LLVM's other include guards seems like a better fix.

[thakis]

Makes sense to me.

JDevlieghere, do you remember why you went with that other approach?

[barannikov88]

llvm/lib/Support/regex_impl.h

108

[hans]

llvm/lib/Support/regex_impl.h

108

Thanks! Will fix when committing.

[hans]

In D150117#4326737, @thakis wrote:

JDevlieghere, do you remember why you went with that other approach?

Let's follow up in https://reviews.llvm.org/D150127 which proposes to remove the old work-around.

llvm/lib/Support/regex_impl.h

  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *  @(#)regex.h 8.1 (Berkeley) 6/2/93
  */
 
-#ifndef _REGEX_H_
-#define _REGEX_H_
+#ifndef LLVM_SUPPORT_REGEX_IMPL_H
+#define LLVM_SUPPORT_REGEX_IMPL_H
 
 #include <sys/types.h>
 typedef off_t llvm_regoff_t;
 typedef struct {
   llvm_regoff_t rm_so;    /* start of match */
   llvm_regoff_t rm_eo;    /* end of match */
 } llvm_regmatch_t;
 
int  llvm_regexec(const llvm_regex_t *, const char *, size_t,
                      llvm_regmatch_t [], int);
 void  llvm_regfree(llvm_regex_t *);
 size_t  llvm_strlcpy(char *dst, const char *src, size_t siz);
 
 #ifdef __cplusplus
 }
 #endif
 
-#endif /* !_REGEX_H_ */
+#endif /* LLVM_SUPPORT_REGEX_IMPL_H */