[PATCH] lto: support --jobserver-style=fifo for recent GNU make

[Martin Liška]

After a long time, GNU make has finally implemented named pipes when
it comes to --jobserver-auth. The traditional approach are
provided opened file descriptors that causes troubles:
https://savannah.gnu.org/bugs/index.php?57242
GNU make commit:
https://git.savannah.gnu.org/cgit/make.git/commit/?id=7ad2593b2d2bb5b9332f4444d8bf93ac6f958bc6

I tested that locally with TOT GNU make and it works:

$ cat Makefile
all:
        g++ tramp3d-v4.ii -c -flto -O2
        g++ tramp3d-v4.o -flto=jobserver

$ MAKE=/tmp/bin/bin/make /tmp/bin/bin/make -j16 --jobserver-style=fifo
g++ tramp3d-v4.ii -c -flto -O2
g++ tramp3d-v4.o -flto=jobserver
(ltrans run in parallel)

Ready to be installed after tests?
Martin

gcc/ChangeLog:

        * gcc.cc (driver::detect_jobserver): Support --jobserver-style=fifo.
        * lto-wrapper.cc (jobserver_active_p): Likewise.
---
 gcc/gcc.cc         | 15 ++++++++++++---
 gcc/lto-wrapper.cc | 20 +++++++++++++++-----
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/gcc/gcc.cc b/gcc/gcc.cc
index 5cbb38560b2..c98407fe03d 100644
--- a/gcc/gcc.cc
+++ b/gcc/gcc.cc
@@ -9182,15 +9182,24 @@ driver::detect_jobserver () const
   const char *makeflags = env.get ("MAKEFLAGS");
   if (makeflags != NULL)
     {
-      const char *needle = "--jobserver-auth=";
-      const char *n = strstr (makeflags, needle);
+      /* Traditionally, GNU make uses opened pieps for jobserver-auth,
+        e.g. --jobserver-auth=3,4.  */
+      const char *pipe_needle = "--jobserver-auth=";
+
+      /* Starting with GNU make 4.4, one can use --jobserver-style=fifo
+        and then named pipe is used: --jobserver-auth=fifo:/tmp/hcsparta.  */
+      const char *fifo_needle = "--jobserver-auth=fifo:";
+      if (strstr (makeflags, fifo_needle) != NULL)
+       return;
+
+      const char *n = strstr (makeflags, pipe_needle);
       if (n != NULL)
        {
          int rfd = -1;
          int wfd = -1;
 
 	  bool jobserver
-           = (sscanf (n + strlen (needle), "%d,%d", &rfd, &wfd) == 2
+           = (sscanf (n + strlen (pipe_needle), "%d,%d", &rfd, &wfd) == 2
               && rfd > 0
               && wfd > 0
               && is_valid_fd (rfd)
diff --git a/gcc/lto-wrapper.cc b/gcc/lto-wrapper.cc
index 795ab74555c..756350d5ace 100644
--- a/gcc/lto-wrapper.cc
+++ b/gcc/lto-wrapper.cc
@@ -1342,27 +1342,37 @@ static const char *
 jobserver_active_p (void)
 {
   #define JS_PREFIX "jobserver is not available: "
-  #define JS_NEEDLE "--jobserver-auth="
+
+  /* Traditionally, GNU make uses opened pieps for jobserver-auth,
+     e.g. --jobserver-auth=3,4.  */
+  #define JS_PIPE_NEEDLE "--jobserver-auth="
+
+  /* Starting with GNU make 4.4, one can use --jobserver-style=fifo
+     and then named pipe is used: --jobserver-auth=fifo:/tmp/hcsparta.  */
+  #define JS_FIFO_NEEDLE "--jobserver-auth=fifo:"
 
   const char *makeflags = getenv ("MAKEFLAGS");
   if (makeflags == NULL)
     return JS_PREFIX "%<MAKEFLAGS%> environment variable is unset";
 
-  const char *n = strstr (makeflags, JS_NEEDLE);
+  if (strstr (makeflags, JS_FIFO_NEEDLE) != NULL)
+    return NULL;
+
+  const char *n = strstr (makeflags, JS_PIPE_NEEDLE);
   if (n == NULL)
-    return JS_PREFIX "%<" JS_NEEDLE "%> is not present in %<MAKEFLAGS%>";
+    return JS_PREFIX "%<" JS_PIPE_NEEDLE "%> is not present in %<MAKEFLAGS%>";
 
   int rfd = -1;
   int wfd = -1;
 
-  if (sscanf (n + strlen (JS_NEEDLE), "%d,%d", &rfd, &wfd) == 2
+  if (sscanf (n + strlen (JS_PIPE_NEEDLE), "%d,%d", &rfd, &wfd) == 2
       && rfd > 0
       && wfd > 0
       && is_valid_fd (rfd)
       && is_valid_fd (wfd))
     return NULL;
   else
-    return JS_PREFIX "cannot access %<" JS_NEEDLE "%> file descriptors";
+    return JS_PREFIX "cannot access %<" JS_PIPE_NEEDLE "%> file descriptors";
 }
 
 /* Print link to -flto documentation with a hint message.  */
--
2.37.1