rustup's libgcc_s_dw2-1.dll breaks gcc under i686-pc-windows-gnu

[tspiteri]

Problem

When I install the stable-i686-pc-windows-gnu toolchain and try to build a crate which calls gcc in its build.rs, the build breaks. For example when trying to build the gmp-mpfr-sys crate under Msys2 32-bit, the build breaks saying that gcc doesn't work.

I managed to reduce the failure to just calling gcc with .rustup/toolchains/stable-i686-pc-windows-gnu/bin in the PATH.

Steps

1. Install stable-i686-pc-windows-gnu toolchain in rustup.

2. Install MSYS2 32-bit gcc. This can be done using:

   • Install MSYS2 using the installer at https://www.msys2.org/

   • Launch the MSYS2 MinGW x86 application which is the 32-bit terminal

   • Install gcc

       pacman -S pacman-mirrors
       pacman -S mingw-w64-x86_64-gcc
     

3. Launch the MSYS2 MinGW x86 application and prepend the rustup toolchain directory to the PATH, something like

    PATH="/c/Users/User/.rustup/toolchains/stable-i686-pc-windows-gnu/bin:$PATH"
   

   with the correct drive for c and username for User.

4. Create the file a.c containing one single line

    int main () { return 0; }
   

5. Try to compile the file using gcc a.c.

Possible Solution(s)

When I rename the file libgcc_s_dw2-1.dll inside .rustup/toolchains/stable-i686-pc-windows-gnu, gcc a.c succeeds.

Notes

No response

Rustup version

rustup 1.25.1 (bb60b1e89 2022-07-12)

Installed toolchains

stable-i686-pc-windows-gnu

[tspiteri]

For what it's worth, the configuration build logs from attempting to build GMP inside gmp-mpfr-sys show the following PATH components:

PATH: /c/Users/User/projects/gmp-mpfr-sys/target/debug/deps
PATH: /c/Users/User/projects/gmp-mpfr-sys/target/debug
PATH: /c/Users/User/.rustup/toolchains/stable-i686-pc-windows-gnu/lib/rustlib/i686-pc-windows-gnu/lib
PATH: /c/Users/User/.rustup/toolchains/stable-i686-pc-windows-gnu/bin
PATH: /mingw32/bin
PATH: /usr/local/bin
PATH: /usr/bin
PATH: /usr/bin
PATH: /c/Windows/System32
PATH: /c/Windows
PATH: /c/Windows/System32/Wbem
PATH: /c/Windows/System32/WindowsPowerShell/v1.0
PATH: /usr/bin/site_perl
PATH: /usr/bin/vendor_perl
PATH: /usr/bin/core_perl
PATH: /c/Users/User/.cargo/bin

The first four PATH components are added by cargo +stable-i686-pc-windows-gnu ... itself.

[tspiteri]

I also tried older i686-gnu toolchains, for example 1.38.0-i686-pc-windows-gnu, and they also fail, which is why I believe the culprit is rustup, not the toolchains. Maybe the paths were appended in 1.24.3 and are now prepended in 1.25? (I cannot really test, as I do not know a way to downgrade rustup to 1.24.3.)

[ChrisDenton]

This seems like it may be caused by the same things as #3036?

[tspiteri]

Ah well, I downgraded to 1.24.3 and I'm getting the same problem.

My suspicion is now that an MSYS2 update has become incompatible with the libgcc_s_dw2-1.dll included with the rust toolchains. And it's failing with old toolchains too, so toolchains that used to work don't work anymore with an up-to-date MSYS2.

[tspiteri]

I've downgraded mingw-w64-i686-{gcc,gcc-libs,libgccjit} to version 11.2.0 and my problem went away. So it seems that the issue is some incompatibility between MSYS2 mingw-w64-i686-gcc >=11.3 and rustc.

[ChrisDenton]

Huh, in that case maybe this issue should be moved over to rustc?

[tspiteri]

I opened an issue in rustc instead; closing.