libbacktrace patch committed

[Ian Lance Taylor via Gcc-patches]

This libbacktrace patch, based on one by Andres Freund, uses the
_pgmptr variable declared on Windows to find the executable file name
if none is specified.  Bootstrapped and ran libbacktrace testsuite on
x86_64-pc-linux-gnu.  Committed to mainline.

Ian

Patch from Andres Freund:
* configure.ac: Check for _pgmptr declaration.
* fileline.c (fileline_initialize): Check for _pgmfptr before
/proc/self/exec.
* configure, config.h.in: Regenerate.

a349ba16f18b66b70c7a1bdb1ab5c5b6247676da
diff --git a/libbacktrace/configure.ac b/libbacktrace/configure.ac
index 39e6bf41e35..72ff2b30053 100644
--- a/libbacktrace/configure.ac
+++ b/libbacktrace/configure.ac
@@ -407,6 +407,9 @@ if test "$have_getexecname" = "yes"; then
   AC_DEFINE(HAVE_GETEXECNAME, 1, [Define if getexecname is available.])
 fi
 
+# Check for _pgmptr variable, contains the executable filename on windows
+AC_CHECK_DECLS([_pgmptr])
+
 # Check for sysctl definitions.
 
 AC_CACHE_CHECK([for KERN_PROC],
diff --git a/libbacktrace/fileline.c b/libbacktrace/fileline.c
index 674bf33cdcf..0e560b44e7a 100644
--- a/libbacktrace/fileline.c
+++ b/libbacktrace/fileline.c
@@ -155,6 +155,16 @@ macho_get_executable_path (struct backtrace_state *state,
 
 #endif /* !defined (HAVE_MACH_O_DYLD_H) */
 
+#if HAVE_DECL__PGMPTR
+
+#define windows_executable_filename() _pgmptr
+
+#else /* !HAVE_DECL__PGMPTR */
+
+#define windows_executable_filename() NULL
+
+#endif /* !HAVE_DECL__PGMPTR */
+
 /* Initialize the fileline information from the executable.  Returns 1
    on success, 0 on failure.  */
 
@@ -192,7 +202,7 @@ fileline_initialize (struct backtrace_state *state,
 
   descriptor = -1;
   called_error_callback = 0;
-  for (pass = 0; pass < 8; ++pass)
+  for (pass = 0; pass < 9; ++pass)
     {
       int does_not_exist;
 
@@ -205,23 +215,28 @@ fileline_initialize (struct backtrace_state *state,
          filename = getexecname ();
          break;
        case 2:
-         filename = "/proc/self/exe";
+         /* Test this before /proc/self/exe, as the latter exists but points
+            to the wine binary (and thus doesn't work).  */
+         filename = windows_executable_filename ();
          break;
        case 3:
-         filename = "/proc/curproc/file";
+         filename = "/proc/self/exe";
          break;
        case 4:
+         filename = "/proc/curproc/file";
+         break;
+       case 5:
          snprintf (buf, sizeof (buf), "/proc/%ld/object/a.out",
                    (long) getpid ());
          filename = buf;
          break;
-       case 5:
+       case 6:
          filename = sysctl_exec_name1 (state, error_callback, data);
          break;
-       case 6:
+       case 7:
          filename = sysctl_exec_name2 (state, error_callback, data);
          break;
-       case 7:
+       case 8:
          filename = macho_get_executable_path (state, error_callback, data);
          break;
        default: