Hi Richard! On Mon, 10 Jun 2013 14:01:53 +0200 (CEST), Richard Biener <[email protected]> wrote: > This fixes one very annoying thing collect2 does when trying to > debug LTO WPA issues. Even with -v you need to wait until all > LTRANS stages completed to see the lto1 -fwpa invocation which > is because collect2 buffers and replays stdout/stderr of ld > (to avoid duplicating that in some cases). But I really want > to see the output immediately but there is no way to do that. > The easiest is to disable the buffering with -debug (that is, > -Wl,-debug to the -flto driver command line). > > Tested with/without -debug. > > Ok for trunk?
> * collect2.c (main): Do not redirect ld stdout/stderr when
> debugging.
> --- gcc/collect2.c (revision 199732)
> +++ gcc/collect2.c (working copy)
> @@ -1189,8 +1189,11 @@ main (int argc, char **argv)
> #ifdef COLLECT_EXPORT_LIST
> export_file = make_temp_file (".x");
> #endif
> - ldout = make_temp_file (".ld");
> - lderrout = make_temp_file (".le");
> + if (!debug)
> + {
> + ldout = make_temp_file (".ld");
> + lderrout = make_temp_file (".le");
> + }
> *c_ptr++ = c_file_name;
> *c_ptr++ = "-x";
> *c_ptr++ = "c";
This change (r199936) is problematic, given the usage of ldout and
lderrout in gcc/tlink.c:do_tlink. If, for -debug, they're not
initialized, they'll be NULL, which in do_tlink, the tlink_execute call
will handle fine (as I understand it), but after that, for example,
dump_ld_file will attempt to fopen (NULL), which will cause a SIGSEGV on
GNU Hurd at least. (Correct me if I'm wrong -- I have not yet read the
relevant standards in detail -- but from what I remember, that's
appropriate: NULL is not a string naming a file.)
I found this when running binutils' gold testsuite:
$ gcc-4.9 -W -Wall -Wstrict-prototypes -Wmissing-prototypes -Wshadow
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -fmerge-constants -g -O2
-fno-use-linker-plugin -o incremental_test -Bgcctestdir/ -Wl,--incremental-full
incremental_test_1.o incremental_test_2.o -v -Wl,-debug
[...]
gcc-4.9: internal compiler error: Segmentation fault (program collect2)
[...]
In do_tlink, the last four uses of ldout and lderrout should be guarded
by NULL and empty string checks (as done in gcc/collect2.c:tool_cleanup),
but I'm not sure what the correct fix is in the »if (ret)« block:
void
do_tlink (char **ld_argv, char **object_lst ATTRIBUTE_UNUSED)
{
int ret = tlink_execute ("ld", ld_argv, ldout, lderrout,
HAVE_GNU_LD && at_file_supplied);
tlink_init ();
if (ret)
{
int i = 0;
/* Until collect does a better job of figuring out which are object
files, assume that everything on the command line could be. */
if (read_repo_files (ld_argv))
while (ret && i++ < MAX_ITERATIONS)
{
if (tlink_verbose >= 3)
{
dump_ld_file (ldout, stdout);
dump_ld_file (lderrout, stderr);
}
demangle_new_symbols ();
if (! scan_linker_output (ldout)
&& ! scan_linker_output (lderrout))
break;
if (! recompile_files ())
break;
if (tlink_verbose)
fprintf (stderr, _("collect: relinking\n"));
ret = tlink_execute ("ld", ld_argv, ldout, lderrout,
HAVE_GNU_LD && at_file_supplied);
}
}
dump_ld_file (ldout, stdout);
unlink (ldout);
dump_ld_file (lderrout, stderr);
unlink (lderrout);
[...]
Grüße,
Thomas
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