On 02/19/2015 08:50 AM, Jakub Jelinek wrote:
On Thu, Feb 19, 2015 at 08:45:08AM -0800, Aldy Hernandez wrote:
[And this time, actually CCing the list :)].
Gentlemen!
Reading in the compiler state for pch (gt_pch_restore) obliterates the
DIE table, and consequently the DW_TAG_GNU_[BE]INCL* DIEs that may have
been in it. This causes inconsistencies when reading in _any_
pre-compiled header into a source file that uses
-feliminate-dwarf2-dups, and consequently already has some
DW_TAG_GNU_[BE]INCL* DIEs.
Normally the DIE table should be empty this early on, especially since
mainline generates dwarf at the end of the compilation unit, but the DIE
table may have DW_TAG_GNU_[BE]INCL* DIEs that were created early by
dwarf2out_start_source_file/etc or it may have the DW_TAG_compile_unit.
I suppose we could merge incoming DIEs with existing DIEs and complicate
our lives, but considering we will probably have to tackle this in the
debug-early work, I propose we disable this combination for now (and
possibly permanently, unless we really care about it).
OK for mainline pending tests?
Wouldn't it be better to disable PCH reading if -feliminate-dwarf2-dups
is used? I mean, fail to read the PCH silently (or with warning for -Wpch
or what the warning is about why PCH couldn't be read or was ignored),
Sure, that sounds reasonable. Patch attached.
perhaps error out if you try to generate PCH with -feliminate-dwarf2-dups?
Well, any PCH file we generate will have some sort of early DIE in it
(at the very least the compilation unit DIE) and we will read these in
at PCH read-in time, obliterating whatever was already there. But most
importantly, with the attached patch we will not use these
DW_TAG_GNU_[BE]INCL* DIEs, since the reader will avoid reading the pch
file. So, I don't think erroring out at output time is necessary.
How does this look?
commit d90a408ad21aa0868cc13de24ea38e210ef78a68
Author: Aldy Hernandez <al...@redhat.com>
Date: Thu Feb 19 07:35:59 2015 -0800
PR debug/46102
* c-pch.c (c_common_valid_pch): Mark PCH file with
-feliminate-dwarf2-dups as invalid.
diff --git a/gcc/c-family/c-pch.c b/gcc/c-family/c-pch.c
index 0ede92a..55163c9 100644
--- a/gcc/c-family/c-pch.c
+++ b/gcc/c-family/c-pch.c
@@ -224,6 +224,19 @@ c_common_valid_pch (cpp_reader *pfile, const char *name,
int fd)
const char *pch_ident;
struct c_pch_validity v;
+ /* We may have outputted a few DIEs corresponding to
+ DW_TAG_GNU_[BE]INCL. Reading the compiler state later will read
+ in these DIEs, and obliterate any DW_TAG_GNU_[BE]INCL the reader
+ may have generated itself. Do not read the PCH if this may
+ happen. */
+ if (flag_eliminate_dwarf2_dups)
+ {
+ if (cpp_get_options (pfile)->warn_invalid_pch)
+ cpp_error (pfile, CPP_DL_WARNING,
+ "%s: cannot be used with -feliminate-dwarf2-dups", name);
+ return 2;
+ }
+
/* Perform a quick test of whether this is a valid
precompiled header for the current language. */
