[Bug ld/12614] New: mingw ld omits needed jump stubs in link involving --start/end-group

2011-03-28 Thread dklprogramming at web dot de 
http://sourceware.org/bugzilla/show_bug.cgi?id=12614

   Summary: mingw ld omits needed jump stubs in link involving
--start/end-group
   Product: binutils
   Version: unspecified
Status: NEW
  Severity: normal
  Priority: P2
 Component: ld
AssignedTo: unassig...@sources.redhat.com
ReportedBy: dklprogramm...@web.de


Created attachment 5337
  --> http://sourceware.org/bugzilla/attachment.cgi?id=5337
Example with makefile

Related to a patch that was applied to ld between binutils 2.17 and 2.18:
"Eliminate redundant jump stubs on windows/cygwin/MinGW"


See also:




It appears that ld accidentally excludes jump stubs from an import library,
when linking like this:
main.o -( libfoo.dll.a test.o -)
where main.o references a symbol from the import library, and test.o uses
a second symbol from the import library. In that case the jump stub for the
second symbol (referenced only by test.o) is not included into the executable.

If only test.o but not main.o reference a symbol in the import library, the
problem does not occur. (Using __declspec(dllimport) on the symbol referenced
in test.o prevents running into this issue completely.)

Here is an example; it requires a toolchain targetting mingw32:

$ cat main.c
void test();
void bar();
void mainCRTStartup() {
test();
bar();
}
$ cat test.c
void foo();
void test() {
foo();
}
$ cat foo.def
LIBRARY foo.dll
EXPORTS
foo
bar
$ i586-mingw32msvc-gcc -Wall -c main.c -o main.o
$ i586-mingw32msvc-gcc -Wall -c test.c -o test.o
$ i586-mingw32msvc-dlltool --input-def foo.def --output-lib libfoo.dll.a
$ i586-mingw32msvc-ld -o good.exe main.o test.o libfoo.dll.a
$ i586-mingw32msvc-ld -o bad.exe main.o "-(" libfoo.dll.a test.o "-)"
$ i586-mingw32msvc-objdump -D good.exe > good-disasm.txt
$ i586-mingw32msvc-objdump -D bad.exe > bad-disasm.txt

Excerpt from good-disasm.txt:

00401000 <_mainCRTStartup>:
  401000:55   push   %ebp
  401001:89 e5mov%esp,%ebp
  401003:83 ec 08 sub$0x8,%esp
  401006:e8 09 00 00 00   call   401014 <_test>
  40100b:e8 14 00 00 00   call   401024 <_bar>
  401010:c9   leave  
  401011:c3   ret
  401012:90   nop
  401013:90   nop

00401014 <_test>:
  401014:55   push   %ebp
  401015:89 e5mov%esp,%ebp
  401017:83 ec 08 sub$0x8,%esp
  40101a:e8 0d 00 00 00   call   40102c <_foo>
  40101f:c9   leave  
  401020:c3   ret
  401021:90   nop
  401022:90   nop
  401023:90   nop

00401024 <_bar>:
  401024:ff 25 34 20 40 00jmp*0x402034
  40102a:90   nop
  40102b:90   nop

0040102c <_foo>:
  40102c:ff 25 38 20 40 00jmp*0x402038
  401032:90   nop
  401033:90   nop

Excerpt from bad-disasm.txt:

00401000 <_mainCRTStartup>:
  401000:55   push   %ebp
  401001:89 e5mov%esp,%ebp
  401003:83 ec 08 sub$0x8,%esp
  401006:e8 11 00 00 00   call   40101c <_test>
  40100b:e8 04 00 00 00   call   401014 <_bar>
  401010:c9   leave  
  401011:c3   ret
  401012:90   nop
  401013:90   nop

00401014 <_bar>:
  401014:ff 25 34 20 40 00jmp*0x402034
  40101a:90   nop
  40101b:90   nop

0040101c <_test>:
  40101c:55   push   %ebp
  40101d:89 e5mov%esp,%ebp
  40101f:83 ec 08 sub$0x8,%esp
  401022:e8 d9 ef bf ff   call   0 <_foo>
  401027:c9   leave  
  401028:c3   ret
  401029:90   nop
  40102a:90   nop
  40102b:90   nop

Notice that in bad.exe the <_foo> stub is not present, and there is a 'call 0'
in <_test>.

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[Bug ld/12614] mingw ld omits needed jump stubs in link involving --start/end-group

2011-04-27 Thread dklprogramming at web dot de 
http://sourceware.org/bugzilla/show_bug.cgi?id=12614

--- Comment #1 from dklprogramming at web dot de 2011-04-27 19:11:59 UTC ---
Hi,

this is my first time hacking the binutils/ld sources, but I think I may have
identified the problem.

There is a block of code in src/ld/emultempl/pe.em that tries to detect
redundant jump stubs and marks them for exclusion. It checks each symbol in the
stub section to find out whether it is used or not. However, only the symbol's
u.undef.next field (in struct bfd_link_hash_entry) is checked to determine
whether the symbol is in the undefined list or not.

This is not enough if the symbol is at the end of the list, because then the
next pointer will be NULL, even though the symbol is in the undefined list. In
the attached patch I have added a check against link_info.hash->undefs_tail to
cover that case.

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[Bug ld/12614] mingw ld omits needed jump stubs in link involving --start/end-group

2011-04-27 Thread dklprogramming at web dot de 
http://sourceware.org/bugzilla/show_bug.cgi?id=12614

--- Comment #2 from dklprogramming at web dot de 2011-04-27 19:14:22 UTC ---
Created attachment 5690
  --> http://sourceware.org/bugzilla/attachment.cgi?id=5690
Proposed patch

ChangeLog ld

* emultempl/pe.em (gld_${EMULATION_NAME}_after_open): Correctly check
whether symbol is in undef list.

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[Bug ld/12614] mingw ld omits needed jump stubs in link involving --start/end-group

2011-04-28 Thread dklprogramming at web dot de 
http://sourceware.org/bugzilla/show_bug.cgi?id=12614

dklprogramming at web dot de changed:

   What|Removed |Added

   Attachment #5690|0   |1
is obsolete||

--- Comment #4 from dklprogramming at web dot de 2011-04-28 13:19:47 UTC ---
Created attachment 5693
  --> http://sourceware.org/bugzilla/attachment.cgi?id=5693
Updated patch

2011-04-28  Daniel C. Klauer  

* emultempl/pe.em (gld_${EMULATION_NAME}_after_open): Correctly check
whether symbol is in undef list.

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[Bug ld/12614] mingw ld omits needed jump stubs in link involving --start/end-group

2011-04-28 Thread dklprogramming at web dot de 
http://sourceware.org/bugzilla/show_bug.cgi?id=12614

--- Comment #5 from dklprogramming at web dot de 2011-04-28 13:23:26 UTC ---
I have updated the patch and also added my name to the changelog item.

Thank you,
Daniel

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