libgo patch committed: For c-archive, install signal handler synchronously

[Ian Lance Taylor]

This patch to libgo ports https://golang.org/cl/18150 from the master
library to the gccgo runtime.  This installs signal handlers
synchronously when building a Go archive, rather than potentially
racing against the main program.  Bootstrapped and ran Go testsuite on
x86_64-pc-linux-gnu.  Committed to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 233290)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-28a9dfbc3cda0bf7fd4f3fb1506c547f6cdf41a5
+22278c6e8ce3982b09111183bc6addf0184bef1f
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: libgo/runtime/go-libmain.c
===================================================================
--- libgo/runtime/go-libmain.c  (revision 232239)
+++ libgo/runtime/go-libmain.c  (working copy)
@@ -59,6 +59,10 @@ initfn (int argc, char **argv, char** en
   struct args *a;
   pthread_t tid;
 
+  runtime_isarchive = true;
+
+  runtime_initsig(true);
+
   a = (struct args *) malloc (sizeof *a);
   if (a == NULL)
     die ("malloc", errno);
@@ -88,8 +92,6 @@ gostart (void *arg)
 {
   struct args *a = (struct args *) arg;
 
-  runtime_isarchive = true;
-
   if (runtime_isstarted)
     return NULL;
   runtime_isstarted = true;
Index: libgo/runtime/proc.c
===================================================================
--- libgo/runtime/proc.c        (revision 233260)
+++ libgo/runtime/proc.c        (working copy)
@@ -1093,7 +1093,7 @@ runtime_mstart(void* mp)
                        runtime_newextram();
                        runtime_needextram = 0;
                }
-               runtime_initsig();
+               runtime_initsig(false);
        }
        
        if(m->mstartfn)
Index: libgo/runtime/runtime.h
===================================================================
--- libgo/runtime/runtime.h     (revision 233260)
+++ libgo/runtime/runtime.h     (working copy)
@@ -550,7 +550,7 @@ void*       runtime_mal(uintptr);
 String runtime_gostring(const byte*);
 String runtime_gostringnocopy(const byte*);
 void   runtime_schedinit(void);
-void   runtime_initsig(void);
+void   runtime_initsig(bool);
 void   runtime_sigenable(uint32 sig);
 void   runtime_sigdisable(uint32 sig);
 void   runtime_sigignore(uint32 sig);
Index: libgo/runtime/signal_unix.c
===================================================================
--- libgo/runtime/signal_unix.c (revision 233110)
+++ libgo/runtime/signal_unix.c (working copy)
@@ -13,11 +13,16 @@
 extern SigTab runtime_sigtab[];
 
 void
-runtime_initsig(void)
+runtime_initsig(bool preinit)
 {
        int32 i;
        SigTab *t;
 
+       // For c-archive/c-shared this is called by go-libmain.c with
+       // preinit == true.
+       if(runtime_isarchive && !preinit)
+               return;
+
        // First call: basic setup.
        for(i = 0; runtime_sigtab[i].sig != -1; i++) {
                t = &runtime_sigtab[i];
@@ -37,6 +42,9 @@ runtime_initsig(void)
                        }
                }
 
+               if(runtime_isarchive && (t->flags&SigPanic) == 0)
+                       continue;
+
                t->flags |= SigHandling;
                runtime_setsig(i, runtime_sighandler, true);
        }