PR 17185

PR 17185 describes a problem with using gdb+guile with libgc 7.4.0.
The symptom is a hang in sigsuspend.
[The thread referenced in the PR has the details.]
It's not clear what the right fix is, or even where the bug is yet.
This patch applies the same workaround Guile has applied.
There is no functionality or real performance loss with this,
and Guile has been using it for awhile.

	* configure.ac: Add check for header gc/gc.h.
	Add check for function setenv.
	* configure: Regenerate.
	* config.in: Regenerate.
	* guile/guile.c (_initialize_guile): Add workaround for libgc 7.4.0.

gdb/ChangeLog

@@ -1,3 +1,12 @@
+2014-07-26  Doug Evans  <xdje42@gmail.com>
+
+	PR 17185
+	* configure.ac: Add check for header gc/gc.h.
+	Add check for function setenv.
+	* configure: Regenerate.
+	* config.in: Regenerate.
+	* guile/guile.c (_initialize_guile): Add workaround for libgc 7.4.0.
+
 2014-07-25  Maciej W. Rozycki  <macro@codesourcery.com>
 
 	* mips-tdep.c (mips_gdbarch_init): Also check the compressed ISA

gdb/config.in

@@ -141,6 +141,9 @@
 /* Define if <sys/procfs.h> has fpregset_t. */
 #undef HAVE_FPREGSET_T
 
+/* Define to 1 if you have the <gc/gc.h> header file. */
+#undef HAVE_GC_GC_H
+
 /* Define to 1 if you have the `getgid' function. */
 #undef HAVE_GETGID
 
@@ -345,6 +348,9 @@
 /* Define to 1 if you have the `scm_new_smob' function. */
 #undef HAVE_SCM_NEW_SMOB
 
+/* Define to 1 if you have the `setenv' function. */
+#undef HAVE_SETENV
+
 /* Define to 1 if you have the `setlocale' function. */
 #undef HAVE_SETLOCALE
 

gdb/configure

@@ -9103,6 +9103,32 @@ fi
 
 
 
+# PR 17185, see if we can get the libgc version to see if we need
+# to apply the workaround.
+for ac_header in gc/gc.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "gc/gc.h" "ac_cv_header_gc_gc_h" "$ac_includes_default"
+if test "x$ac_cv_header_gc_gc_h" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_GC_GC_H 1
+_ACEOF
+
+fi
+
+done
+
+for ac_func in setenv
+do :
+  ac_fn_c_check_func "$LINENO" "setenv" "ac_cv_func_setenv"
+if test "x$ac_cv_func_setenv" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_SETENV 1
+_ACEOF
+
+fi
+done
+
+
 # --------------------- #
 # Check for libmcheck.  #
 # --------------------- #

gdb/configure.ac

@@ -1218,6 +1218,11 @@ fi
 AC_SUBST(GUILE_CPPFLAGS)
 AC_SUBST(GUILE_LIBS)
 
+# PR 17185, see if we can get the libgc version to see if we need
+# to apply the workaround.
+AC_CHECK_HEADERS(gc/gc.h)
+AC_CHECK_FUNCS([setenv])
+
 # --------------------- #
 # Check for libmcheck.  #
 # --------------------- #

gdb/guile/guile.c

@@ -35,6 +35,9 @@
 #ifdef HAVE_GUILE
 #include "guile.h"
 #include "guile-internal.h"
+#ifdef HAVE_GC_GC_H
+#include <gc/gc.h> /* PR 17185 */
+#endif
 #endif
 
 /* The Guile version we're using.
@@ -750,6 +753,18 @@ _initialize_guile (void)
      side to define module "gdb" which imports "_gdb".  There is evidently no
      similar convention in Guile so we skip this.  */
 
+  /* PR 17185 There are problems with using libgc 7.4.0.
+     Copy over the workaround Guile uses (Guile is working around a different
+     problem, but the workaround is the same).  */
+#if (GC_VERSION_MAJOR == 7 && GC_VERSION_MINOR == 4 && GC_VERSION_MICRO == 0)
+  /* The bug is only known to appear with pthreads.  We assume any system
+     using pthreads also uses setenv (and not putenv).  That is why we don't
+     have a similar call to putenv here.  */
+#if defined (HAVE_SETENV)
+  setenv ("GC_MARKERS", "1", 1);
+#endif
+#endif
+
   /* scm_with_guile is the most portable way to initialize Guile.
      Plus we need to initialize the Guile support while in Guile mode
      (e.g., called from within a call to scm_with_guile).  */