Bug 69821 - -fdebug-prefix-map doesn't affect gcc command line switches in DWARF DW_AT_producer.
Summary: -fdebug-prefix-map doesn't affect gcc command line switches in DWARF DW_AT_pr...
Status: RESOLVED FIXED
Alias: None
Product: gcc
Classification: Unclassified
Component: other (show other bugs)
Version: 5.3.0
: P3 normal
Target Milestone: 6.0
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2016-02-15 06:38 UTC by hongxu jia
Modified: 2016-02-16 01:16 UTC (History)
3 users (show)

See Also:
Host:
Target:
Build:
Known to work:
Known to fail:
Last reconfirmed:

Attachments
add option (1.35 KB, patch)
2016-02-15 07:16 UTC, hongxu jia 		Details | Diff
View All Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description hongxu jia 2016-02-15 06:38:15 UTC 
Hi all,

I come from OpenEmbedded community (https://www.yoctoproject.org/),
thanks the powerful gcc, it helps us to do lots of compiling staff.
While cross compilation, we add '-g' to record debugging info,
and lots of build path existed in debugging info. We do not want to
expose the build path to others. So add '-fdebug-prefix-map=old=new'
to replace the build path with target path.

But the option '-fdebug-prefix-map=old=new' itself which included
build path still exists in gcc command line switches in DWARF
DW_AT_producer. I know we could use '-gno-record-gcc-switches' to
not record all gcc command line switches in DWARF DW_AT_producer.
But we would like to keep the others and only remove
'-fdebug-prefix-map=old=new'.

So I suggested to add a new option '-gno-record-debug-prefix-map'
which don't record '-fdebug-prefix-map' in gcc command line switches
in DWARF DW_AT_producer.

Thanks
Hongxu
Comment 1 hongxu jia 2016-02-15 07:16:23 UTC 
Created attachment 37691 [details]
add option

Compile without this fix:
objdump -g packages-split/lib32-glibc-dev/usr/lib/gcrt1.o
...
|    <5f>   DW_AT_producer    : (indirect string, offset: 0x1b): GNU C99 5.3.0
-m32-march=core2 -mtune=core2 -msse3 -mfpmath=sse -mpreferred-stack-boundary=4
-g -O2 -std=gnu99 -fgnu89-inline -fdebug-prefix-map=/buildarea/raid0/hjia/buil
d-20160127-yocto-buildpath-2/tmp/sysroots/lib32-qemux86-64=
-feliminate-unused-debug-types -fmerge-all-constants -frounding-math
-ftls-model=initial-exec
...

Compile with this fix:
objdump -g packages-split/lib32-glibc-dev/usr/lib/gcrt1.o
...
|    <5f>   DW_AT_producer    : (indirect string, offset: 0xa1): GNU C99 5.3.0
-m32 -march=core2 -mtune=core2 -msse3 -mfpmath=sse -mpreferred-stack-boundary=4
-g -O2 -std=gnu99 -fgnu89-inline -feliminate-unused-debug-types -fmerge-all-constants
-frounding-math -ftls-model=initial-exec
...
Comment 2 Andrew Pinski 2016-02-15 07:25:56 UTC 
Patches should be sent to gcc-patches@.
Comment 3 hongxu jia 2016-02-15 08:10:47 UTC 
(In reply to Andrew Pinski from comment #2)
> Patches should be sent to gcc-patches@.

Got it

//Hongxu
Comment 4 Richard Biener 2016-02-15 12:49:58 UTC 
I think it makes sense to omit this by default.  In fact it is already in GCC 6.

      case OPT_fdebug_prefix_map_:
        /* Ignore these.  */
Comment 5 Jakub Jelinek 2016-02-15 13:18:15 UTC 
Indeed.  This has been fixed with r231835.
Comment 6 Bernd Schmidt 2016-02-15 14:43:27 UTC 
Should we backport this to 5?
Comment 7 Jakub Jelinek 2016-02-15 14:52:05 UTC 
It is not a regression and is user visible change, so I think changing it just in GCC 6 is sufficient.
Comment 8 hongxu jia 2016-02-16 01:16:09 UTC 
(In reply to Jakub Jelinek from comment #7)
> It is not a regression and is user visible change, so I think changing it
> just in GCC 6 is sufficient.

Got it, thanks for pointing it out.
I will backport to our Yocto.

//Hongxu