diff mbox

[patch+7.9] compile: Filter out -fpreprocessed

Message ID 20150116224234.GA6176@host2.jankratochvil.net
State New, archived
Headers

Commit Message

Jan Kratochvil Jan. 16, 2015, 10:42 p.m. UTC 
  Hi,

with global system gcc-5.0 if one also installs ccache (needing a different
patch 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 - I may post a gcc
patch for it.  But even if it gets accepted there are already built inferiors
out there which GDB could be compatible (for the 'compile' mode) with.

gdb.compile/*.exp PASSes for it on {x86_64,x86_64-m32}-fedora22pre-linux-gnu.


Thanks,
Jan
gdb/ChangeLog
2015-01-16  Jan Kratochvil  <jan.kratochvil@redhat.com>

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

Comments

Doug Evans Feb. 3, 2015, 6:50 p.m. UTC | #1 
On Fri, Jan 16, 2015 at 2:42 PM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> [...]
> It is wrong that gcc puts -fpreprocessed into DW_AT_producer - I may post a gcc
> patch for it.

Hi.
I wasn't aware there are now rules for what can and cannot go in DW_AT_producer.
DW_AT_producer has gone from being informational to having a formal
spec (in the sense that something will break if, for example, a
particular option is mentioned).
Is this spec written down somewhere? [At least guidelines for what
things may lead to breakage?]
Jan Kratochvil Feb. 3, 2015, 6:59 p.m. UTC | #2 
On Tue, 03 Feb 2015 19:50:40 +0100, Doug Evans wrote:
> On Fri, Jan 16, 2015 at 2:42 PM, Jan Kratochvil
> <jan.kratochvil@redhat.com> wrote:
> > [...]
> > It is wrong that gcc puts -fpreprocessed into DW_AT_producer - I may post a gcc
> > patch for it.
> 
> Hi.
> I wasn't aware there are now rules for what can and cannot go in DW_AT_producer.
> DW_AT_producer has gone from being informational to having a formal
> spec (in the sense that something will break if, for example, a
> particular option is mentioned).
> Is this spec written down somewhere? [At least guidelines for what
> things may lead to breakage?]

No. Do you have a suggestion where to put it? Should it be only a GNU
extension or should it be even DWARF-standardized?


Jan
Mark Wielaard Feb. 3, 2015, 7:10 p.m. UTC | #3 
On Tue, 2015-02-03 at 19:59 +0100, Jan Kratochvil wrote:
> On Tue, 03 Feb 2015 19:50:40 +0100, Doug Evans wrote:
> > On Fri, Jan 16, 2015 at 2:42 PM, Jan Kratochvil
> > <jan.kratochvil@redhat.com> wrote:
> > > [...]
> > > It is wrong that gcc puts -fpreprocessed into DW_AT_producer - I may post a gcc
> > > patch for it.
> > 
> > I wasn't aware there are now rules for what can and cannot go in DW_AT_producer.
> > DW_AT_producer has gone from being informational to having a formal
> > spec (in the sense that something will break if, for example, a
> > particular option is mentioned).
> > Is this spec written down somewhere? [At least guidelines for what
> > things may lead to breakage?]
> 
> No. Do you have a suggestion where to put it? Should it be only a GNU
> extension or should it be even DWARF-standardized?

The gcc documentation describes it:
https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html

-grecord-gcc-switches
        This switch causes the command-line options used to invoke the
        compiler that may affect code generation to be appended to the
        DW_AT_producer attribute in DWARF debugging information. The
        options are concatenated with spaces separating them from each
        other and from the compiler version. See also
        -frecord-gcc-switches for another way of storing compiler
        options into the object file. This is the default.

-gno-record-gcc-switches
        Disallow appending command-line options to the DW_AT_producer
        attribute in DWARF debugging information.

So Jan is right that gcc adding -fpreprocessed, which doesn't affect
code generation, but is a preprocessor option, shouldn't be there.

Cheers,

Mark
Doug Evans Feb. 4, 2015, 6:15 p.m. UTC | #4 
On Tue, Feb 3, 2015 at 11:10 AM, Mark Wielaard <mjw@redhat.com> wrote:
> On Tue, 2015-02-03 at 19:59 +0100, Jan Kratochvil wrote:
>> On Tue, 03 Feb 2015 19:50:40 +0100, Doug Evans wrote:
>> > On Fri, Jan 16, 2015 at 2:42 PM, Jan Kratochvil
>> > <jan.kratochvil@redhat.com> wrote:
>> > > [...]
>> > > It is wrong that gcc puts -fpreprocessed into DW_AT_producer - I may post a gcc
>> > > patch for it.
>> >
>> > I wasn't aware there are now rules for what can and cannot go in DW_AT_producer.
>> > DW_AT_producer has gone from being informational to having a formal
>> > spec (in the sense that something will break if, for example, a
>> > particular option is mentioned).
>> > Is this spec written down somewhere? [At least guidelines for what
>> > things may lead to breakage?]
>>
>> No. Do you have a suggestion where to put it? Should it be only a GNU
>> extension or should it be even DWARF-standardized?
>
> The gcc documentation describes it:
> https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
>
> -grecord-gcc-switches
>         This switch causes the command-line options used to invoke the
>         compiler that may affect code generation to be appended to the
>         DW_AT_producer attribute in DWARF debugging information. The
>         options are concatenated with spaces separating them from each
>         other and from the compiler version. See also
>         -frecord-gcc-switches for another way of storing compiler
>         options into the object file. This is the default.
>
> -gno-record-gcc-switches
>         Disallow appending command-line options to the DW_AT_producer
>         attribute in DWARF debugging information.
>
> So Jan is right that gcc adding -fpreprocessed, which doesn't affect
> code generation, but is a preprocessor option, shouldn't be there.

Thanks.

Still, there's no hint to the reader that things may break if certain rules
are not followed. It still seems like it's for informational purposes for
human readers, with no suggestion that programs use this information too.

[For completeness sake, I'm setting aside the compiler and version string.
That seemed common enough knowledge to not need documentation
as much as this does.  I realize we're now talking about -grecord-gcc-switches,
but this thread was originally about DW_AT_producer in general.]
diff mbox

Patch

diff --git a/gdb/compile/compile.c b/gdb/compile/compile.c
index ccac49d..ecbd15c 100644
--- a/gdb/compile/compile.c
+++ b/gdb/compile/compile.c
@@ -324,6 +324,26 @@  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)
+	{
+	  (*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 +366,7 @@  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);
     }