OS: Win7 SP1
Toolchain: Mingw-w64 i686-6.2.0-release-win32-dwarf-rt_v5-rev1
GCC: 4.8.x - 6.2.0
Binutils: 2.21 - 2.25.1
MinGW: official and w64, 4.x - 5.0.1
Threading and except: all (dw2/sjlj/seh + win32/posix)
Consider a dll whose base address is overlapped with an existing module, so
that the operating system must relocate it, or for another word, rebase it, to
work. Relocation is the fundamental part of the security feature ASLR and is
enabled by default since Windows Vista. When ASLR is enabled, all executables
are relocated.
BUT, After relocation, the compiled DLL fails to load at all. That's to say,
the compiled DLL is broken.
Minimal case:
=====================
testexe.c
=====================
#include <stdio.h>
__declspec(dllimport) int a();
int main() {
a();
printf("hello world\n");
return 0;
}
=====================
testdll.c
=====================
__declspec(dllexport) int a() {return 0;}
=====================
test.def
=====================
EXPORTS
a
=====================
makefile
=====================
all: test.dll test.exe
clean:
rm test.exe test.dll libtest.a
test.exe: testexe.c
gcc -o $@ $^ libtest.a -Wl,--image-base,0x400000
test.dll: testdll.c
dllwrap -o $@ $^ --def test.def --implib libtest.a
-Wl,--image-base,0x400000
=====================
Case end. Also see the attachment. In this case, test.exe refuses to work with
error 0xC0000005 because test.dll fails to load.
Not only x86-dw2 builds produces the broken DLL, but x86-sjlj, x64-sjlj,
x64-seh, all builds since 2010, that's to say, gcc 4.8.x to 6.2 with binutils
2.21 to 2.25.1, have the same problem. OH MY GOD.
For I know, the only working MinGW bundle is the version comes with Dev-C++
4.9.9.2 in 2005 (GCC 3.4.2 + binutils 2.15.91 + original MinGW32 + dw2 + win32).
Nothing is wrong when using Microsoft Visual C++.
I don't know what's wrong, GCC or binutils?. I can't submit bug to GCC bugzilla
because it is rejecting new account creation. It's really annoying to see GCC
produced broken DLLs and showing 0xC0000005 frequently and randomly. Could
anyone help me?
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