compile: Filter out -fpreprocessed

With global system gcc-5.0 if one also installs ccache (needing a different
patch
	https://bugzilla.samba.org/show_bug.cgi?id=11060
for -fplugin=libcc1plugin) it breaks as GDB will read from inferior
DW_AT_producer containing -fpreprocessed (due to ccache used to compile the
inferior).
    <c>   DW_AT_producer    : (indirect string, offset: 0x52): GNU C11 5.0.0 20150114 (Red Hat 5.0.0-0.1) -fpreprocessed -mtune=generic -
march=x86-64 -g

It is wrong that gcc puts -fpreprocessed into DW_AT_producer - fixed it in
trunk GCCs:
	https://gcc.gnu.org/ml/gcc-patches/2015-01/msg01495.html
But even with that fix there are already built inferiors out there which GDB
could be compatible (for the 'compile' mode) with.

gdb/ChangeLog
2015-02-03  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Filter out inferior gcc option -fpreprocessed.
	* compile/compile.c (filter_args): New function.
	(get_args): Use it.

2 files changed, 28 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d40e1e0e244..5cca93ef982 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2015-02-03  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	Filter out inferior gcc option -fpreprocessed.
+	* compile/compile.c (filter_args): New function.
+	(get_args): Use it.
+
 2015-02-02  Joel Brobecker  <brobecker@adacore.com>
 
 	PR gdb/17856:
diff --git a/gdb/compile/compile.c b/gdb/compile/compile.c
index 70b6d44cd20..c204a135ef2 100644
--- a/gdb/compile/compile.c
+++ b/gdb/compile/compile.c
@@ -324,6 +324,27 @@ get_selected_pc_producer_options (void)
   return cs;
 }
 
+/* Filter out unwanted options from *ARGCP and ARGV.  */
+
+static void
+filter_args (int *argcp, char **argv)
+{
+  char **destv;
+
+  for (destv = argv; *argv != NULL; argv++)
+    {
+      /* -fpreprocessed may get in commonly from ccache.  */
+      if (strcmp (*argv, "-fpreprocessed") == 0)
+	{
+	  xfree (*argv);
+	  (*argcp)--;
+	  continue;
+	}
+      *destv++ = *argv;
+    }
+  *destv = NULL;
+}
+
 /* Produce final vector of GCC compilation options.  First element is target
    size ("-m64", "-m32" etc.), optionally followed by DW_AT_producer options
    and then compile-args string GDB variable.  */
@@ -346,6 +367,7 @@ get_args (const struct compile_instance *compiler, struct gdbarch *gdbarch,
       char **argv_producer;
 
       build_argc_argv (cs_producer_options, &argc_producer, &argv_producer);
+      filter_args (&argc_producer, argv_producer);
       append_args (argcp, argvp, argc_producer, argv_producer);
       freeargv (argv_producer);
     }