ASLR is now enabled for GCC binaries and it breaks PCH

[bustercopley]

The binaries in the new gcc-9.2.0-1 packages have ASLR enabled in their PE headers. This breaks using precompiled headers, as they can no longer be mapped at a predictable address. The previous package had 'good' binaries, with ASLR disabled. (This isn't a change in the package itself. I rebuilt the 9.1.0-3 package, and the resulting binaries were 'bad'.)
I raised this on the GCC bug tracker[1].

For the GCC 9.1.0-3 packages (assuming they're still in your cache):

pacman -U /var/cache/pacman/pkg/mingw-w64-x86_64-{gcc-9.1.0-3,gcc-libs-9.1.0-3}-any.pkg.tar.xz --noconfirm
objdump -p /mingw64/lib/gcc/x86_64-w64-mingw32/9.1.0/cc1.exe | grep DllCharacteristics

Output:

DllCharacteristics	00000000

For the GCC 9.2.0-1 packages:

pacman -U /var/cache/pacman/pkg/mingw-w64-x86_64-{gcc-9.2.0-1,gcc-libs-9.2.0-1}-any.pkg.tar.xz --noconfirm
objdump -p /mingw64/lib/gcc/x86_64-w64-mingw32/9.2.0/cc1.exe | grep DllCharacteristics

Output:

DllCharacteristics	00000160

Hex 160 means[2]:
0x040 (IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE) (i.e., ASLR enabled)
| 0x100 (IMAGE_DLLCHARACTERISTICS_NX_COMPAT) (i.e., DEP enabled)
| 0x020 (??)

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91440
[2] https://docs.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-image_optional_header32

[Alexpux]

@bustercopley fixed by 2602139

[Lord-Nightmare]

@bustercopley fixed by 2602139

This did not fix the PCH issues encountered by the MAME project, as far as I can tell. This changed the ASLR/DEP build flags for binutils, but the issue remains with PCH not functioning with the mingw-w64-x86_64-gcc-9.2.0-1-any.pkg.tar.xz package. Everything works fine with gcc 9.1.0-3 x86_64

"
Compiling src/mame/drivers/aristmk5.cpp...
internal error in mingw32_gt_pch_use_address, at config/i386/host-mingw32.c:186: MapViewOfFileEx: Attempt to access invalid address.
: fatal error: had to relocate PCH
compilation terminated.
"

[bustercopley]

Until a new release of the gcc package comes out, workarounds are to remove the ASLR flag from cc1.exe and cc1plus.exe (e.g., using setdllcharacteristics, which you might prefer to compile for yourself) or rebuild gcc from the existing PKGBUILD script (having updated your binutils).

[Lord-Nightmare]

With the updated gcc-9.2.0-2 packages released on 20190829, this is now fixed, at least for my workload.