[Bug gcov-profile/43341] New: pragma pack changes padding in struct gcov_info on 64-bit archs

[Bug gcov-profile/43341] New: pragma pack changes padding in struct gcov_info on 64-bit archs

[amonakov at gcc dot gnu dot org]

cat <<EOF > t.c
int foo(){}
#pragma pack(1)
EOF

gcc -S -fprofile-generate t.c
grep '^\.LPBX' -A 2 t.s

.LPBX0:
        .long   875574314
        .quad   0

The padding ('.zero 4') between .long and .quad that correspond to the first
two fields of struct gcov_info (an int and a ptr) is gone.  This makes building
Firefox with profile feedback impossible on amd64.  At least gcc-4.[1345]
behave this way.


-- 
           Summary: pragma pack changes padding in struct gcov_info on 64-
                    bit archs
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: amonakov at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43341

[Bug gcov-profile/43341] pragma pack changes padding in struct gcov_info on 64-bit archs

[amonakov at gcc dot gnu dot org]

------- Comment #1 from amonakov at gcc dot gnu dot org  2010-04-21 16:43 -------
Created an attachment (id=20455)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20455&action=view)
proposed patch


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43341

[Bug gcov-profile/43341] pragma pack changes padding in struct gcov_info on 64-bit archs

[amonakov at gcc dot gnu dot org]

------- Comment #2 from amonakov at gcc dot gnu dot org  2010-04-21 16:45 -------
*** Bug 43825 has been marked as a duplicate of this bug. ***


-- 

amonakov at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tglek at mozilla dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43341

[Bug gcov-profile/43341] pragma pack changes padding in struct gcov_info on 64-bit archs

[amonakov at gcc dot gnu dot org]

------- Comment #3 from amonakov at gcc dot gnu dot org  2010-04-21 16:54 -------
(In reply to comment #1)
> Created an attachment (id=20455)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20455&action=view) [edit]
> proposed patch
> 

GCC generates gcov structures at runtime, and #pragma pack(1) in the source
file affects their layout.  We probably can reset the alignment in
create_coverage to avoid that.  The above patch implements a different approach
-- it rearranges structure fields and manually sets alignment so that layout
does not depend on current structure packing.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43341