GNOME Evolution contains several interdependent libraries, so on
Cygwin/MinGW the build creates artificial import libraries with dlltool
from .def files. While trying to build 2.28 I came across a possible
incompatibility between the implib generated by dlltool and auto-import
linkage:
$ gcc -shared -Wl,--out-implib,libtest.dll.a -o cygtest.dll libtest.c
Creating library file: libtest.dll.a
$ nm libtest.dll.a | grep -v ' [bdit] '
d000003.o:
00000000 I _cygtest_dll_iname
d000000.o:
00000000 I __head_cygtest_dll
U _cygtest_dll_iname
d000002.o:
U __head_cygtest_dll
00000000 I __imp__test_func
00000000 T _test_func
d000001.o:
U __head_cygtest_dll
00000000 I __imp__test_data
00000000 I __nm__test_data
$ gcc -o test.exe test.c libtest.dll.a
# now let's try with dlltool
$ dlltool --dllname cygtest.dll --input-def libtest.def --output-lib
libtest.dll.a
$ nm libtest.dll.a | grep -v ' [bdit] '
deobt.o:
00000000 I __libtest_dll_a_iname
deobh.o:
00000000 I __head_libtest_dll_a
U __libtest_dll_a_iname
deobs00001.o:
U __head_libtest_dll_a
00000000 I __imp__test_func
00000000 T _test_func
deobs00000.o:
U __head_libtest_dll_a
00000000 I __imp__test_data
# Note no __nm__test_data auto-import here
$ gcc -o test.exe test.c libtest.dll.a
fu000001.o:(.idata$2+0xc): undefined reference to `_libtest_dll_a_iname'
nmth000000.o:(.idata$4+0x0): undefined reference to `__nm__test_data'
collect2: ld returned 1 exit status
Yaakov
__declspec(dllexport) int test_data = 42;
__declspec(dllexport) int test_func(void) { return test_data; }
EXPORTS
test_func
test_data DATA
extern int test_data;
extern int test_func(void);
int
main(void) {
int foo = test_data;
test_func();
return 0;
}
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