Check for and use gettid() directly if available; glibc 2.30 and later

provides a wrapper for the system call:

* configure.in: Check for gettid() and define HAVE_SYS_GETTID if
  gettid() is only usable via syscall().

* server/log.c (log_tid): Use gettid() directly if available.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1879591 13f79535-47bb-0310-9956-ffa450edef68
(cherry picked from commit 33d99cf)

configure.in

@@ -501,22 +501,26 @@ prctl \
 timegm \
 getpgid \
 fopen64 \
-getloadavg
+getloadavg \
+gettid
 )
 
 dnl confirm that a void pointer is large enough to store a long integer
 APACHE_CHECK_VOID_PTR_LEN
 
-AC_CACHE_CHECK([for gettid()], ac_cv_gettid,
+if test $ac_cv_func_gettid = no; then
+  # On Linux before glibc 2.30, gettid() is only usable via syscall()
+  AC_CACHE_CHECK([for gettid() via syscall], ap_cv_gettid,
 [AC_TRY_RUN(#define _GNU_SOURCE
 #include <unistd.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
 int main(int argc, char **argv) {
 pid_t t = syscall(SYS_gettid); return t == -1 ? 1 : 0; },
-[ac_cv_gettid=yes], [ac_cv_gettid=no], [ac_cv_gettid=no])])
-if test "$ac_cv_gettid" = "yes"; then
-    AC_DEFINE(HAVE_GETTID, 1, [Define if you have gettid()])
+  [ap_cv_gettid=yes], [ap_cv_gettid=no], [ap_cv_gettid=no])])
+  if test "$ap_cv_gettid" = "yes"; then
+      AC_DEFINE(HAVE_SYS_GETTID, 1, [Define if you have gettid() via syscall()])
+  fi
 fi
 
 dnl ## Check for the tm_gmtoff field in struct tm to get the timezone diffs

server/log.c

@@ -55,7 +55,7 @@
 #include "ap_mpm.h"
 #include "ap_listen.h"
 
-#if HAVE_GETTID
+#ifdef HAVE_SYS_GETTID
 #include <sys/syscall.h>
 #include <sys/types.h>
 #endif
@@ -627,14 +627,18 @@ static int log_tid(const ap_errorlog_info *info, const char *arg,
 #if APR_HAS_THREADS
     int result;
 #endif
-#if HAVE_GETTID
+#if defined(HAVE_GETTID) || defined(HAVE_SYS_GETTID)
     if (arg && *arg == 'g') {
+#ifdef HAVE_GETTID
+        pid_t tid = gettid();
+#else
         pid_t tid = syscall(SYS_gettid);
+#endif
         if (tid == -1)
             return 0;
         return apr_snprintf(buf, buflen, "%"APR_PID_T_FMT, tid);
     }
-#endif
+#endif /* HAVE_GETTID || HAVE_SYS_GETTID */
 #if APR_HAS_THREADS
     if (ap_mpm_query(AP_MPMQ_IS_THREADED, &result) == APR_SUCCESS
         && result != AP_MPMQ_NOT_SUPPORTED)