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"
<http://sourceware.org/ml/binutils/2007-01/msg00162.html>
See also:
<http://sourceware.org/cgi-bin/cvsweb.cgi/src/ld/pe-dll.c?cvsroot=src#rev1.95>
<http://sourceware.org/git/?p=binutils.git;a=commit;h=6fd5362b96f51a2763e1a55e6cc78e604f369957>
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 e5 mov %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 e5 mov %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 00 jmp *0x402034
40102a: 90 nop
40102b: 90 nop
0040102c <_foo>:
40102c: ff 25 38 20 40 00 jmp *0x402038
401032: 90 nop
401033: 90 nop
Excerpt from bad-disasm.txt:
00401000 <_mainCRTStartup>:
401000: 55 push %ebp
401001: 89 e5 mov %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 00 jmp *0x402034
40101a: 90 nop
40101b: 90 nop
0040101c <_test>:
40101c: 55 push %ebp
40101d: 89 e5 mov %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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