Mail Archives: cygwin/2005/09/15/09:10:41
Hi!
I have been looking at a failure in the testsuite in
libtool-cvs which I have reduced to the following
script. I have included the approximate output from
any program execed by it in comments along with
comments as to what is going wrong.
$ gcc --version | head -1
gcc (GCC) 3.4.4 (cygming special) (gdc 0.12, using dmd 0.125)
$ ld --version | head -1
GNU ld version 2.16.91 20050610
Etc etc yada yada updated the Cygwin installation the
other day...
This limitation is perhaps already known?
Cheers,
Peter
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#!/bin/bash
run ()
{
echo $*
eval $*
}
cat << EOF > a.c
const char* v7 = "foo";
EOF
cat << EOF > main.c
extern const char *v7;
int main(void)
{
return *v7 - 'f';
}
EOF
cat << EOF > a.def
EXPORTS
v7
EOF
run gcc -c a.c -o a.o
run gcc -c main.c -o main.o
run gcc -shared a.def a.o -o a.dll -Wl,--out-implib,a.bad.lib
#Creating library file: a.bad.lib
run gcc -o bad main.o a.bad.lib
run ./bad
#Segmentation fault (core dumped)
echo returns: $?
#returns: 139
run cp a.dll a.temp.dll
# Experiments reveal that removing a.def from the dll linking
# stage makes it work, like this:
run gcc -shared a.o -o a.dll -Wl,--out-implib,a.good.lib
#Creating library file: a.good.lib
run gcc -o good main.o a.good.lib
#Info: resolving _v7 by linking to __imp__v7 (auto-import)
run ./good
echo returns: $?
#returns: 0
# Further experiments reveal that it is the import lib that is
# the culprit (as the missing Info message in the failing run
# hints at), like this:
run ./bad
#Segmentation fault (core dumped)
echo returns: $?
#returns: 139
# I.e. The exe generated with the bad import lib fails even
# if used with the known working dll.
run cp a.temp.dll a.dll
run ./good
echo returns: $?
#returns: 0
# I.e. The exe generated with the good import lib succeeds even
# if used with the dll from the failing run. So the dll isn't
# bad.
# Ergo, the import lib is bad. Comparing nm output from the two
# import libs reveals a significant difference:
run "nm a.bad.lib > a.bad.nm"
run "nm a.good.lib > a.good.nm"
run diff a.bad.nm a.good.nm
#23c23
#< 00000000 T _v7
#---
#> 00000000 I __nm__v7
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