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"zig cc a.c" produces no output file, which breaks autoconf (probably an LLVM 15.0.0 regression) #12858

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williamstein opened this issue Sep 15, 2022 · 1 comment · Fixed by #12905
Closed

"zig cc a.c" produces no output file, which breaks autoconf (probably an LLVM 15.0.0 regression) #12858

williamstein opened this issue Sep 15, 2022 · 1 comment · Fixed by #12905
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bug Observed behavior contradicts documented or intended behavior regression It worked in a previous version of Zig, but stopped working. zig cc Zig as a drop-in C compiler feature
Milestone
0.10.0

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@williamstein
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williamstein commented Sep 15, 2022 •
edited

Zig Version

0.10.0-dev.4060+61aaef0b0

Steps to Reproduce

  1. Create a file a.c with contents int main() { return 0; }
  2. Type zig cc a.c
  3. NO FILE IS CREATED

Expected Behavior

The file a.out should be created.

Actual Behavior

No output file at all is created.

I noticed this when trying to use autoconf to build a simple C program (lzma in this case), but it would immediately break pretty much all use of autoconf, whose most basic test is to build a trivialconftest.c and check for one of the following output files (copied from autoconf source code);

# The possible output files:
ac_files="a.out conftest.exe conftest a.exe a_out.exe b.out conftest.*"

Anyway, this is a really serious bug. I've rarely hit a bug I couldn't work around, but this would be painful, and require writing wrapper scripts to replace zig cc a.c with zig cc a.c -o a.out, etc. That is a bit too much to get right.
@williamstein williamstein added the bug Observed behavior contradicts documented or intended behavior label Sep 15, 2022
@motiejus
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motiejus commented Sep 19, 2022 •
edited

This was caused by fda6d44 ; rolling it back brings our precious a.out back.

motiejus referenced this issue Sep 19, 2022
@andrewrk
zig cc: do not enable the cache for link operations
fda6d44 
This commit makes `zig cc` match the equivalent behavior of
`zig build-exe` with regards to caching. That is - it will cache
individual .c to .o compilations (with the usual exceptions), but will
always repeat the linking process so that incremental linking has a
chance to happen.

Perhaps a future enhancement will provide a way to get the old behavior,
but I suspect this new behavior will be preferred by everyone, because
it is closer to what C compilers do. Note that the old behavior can be
obtained by switching to `zig build-exe` instead of `zig cc` and using
the `--enable-cache` parameter.

Closes #12317
@motiejus motiejus mentioned this issue Sep 19, 2022
Merged
motiejus added a commit to motiejus/zig that referenced this issue Sep 19, 2022
@motiejus
zig cc: emit to a.out if outpath is unspecified
263d050 
If `-o` is not specified for `zig cc` for linking, it should emit the
`a.out` (or equivalent) to the current directory. So then this:

    $ zig cc test.c

Should result in `./a.out`.

If directory is omitted from `Compilation.EmitLoc`, it will default to
the cache directory later in the compilation chain, which will result
in `a.out` missing in the current directory.

If we specify the directory to `Compilation.EmitLoc`, it will be
handled, allegedly, correctly.

Fixes ziglang#12858
@andrewrk andrewrk added the regression It worked in a previous version of Zig, but stopped working. label Sep 19, 2022
@andrewrk andrewrk added this to the 0.10.0 milestone Sep 19, 2022
andrewrk pushed a commit that referenced this issue Sep 19, 2022
@motiejus @andrewrk
zig cc: emit to a.out if outpath is unspecified
4521456 
If `-o` is not specified for `zig cc` for linking, it should emit the
`a.out` (or equivalent) to the current directory. So then this:

    $ zig cc test.c

Should result in `./a.out`.

If directory is omitted from `Compilation.EmitLoc`, it will default to
the cache directory later in the compilation chain, which will result
in `a.out` missing in the current directory.

If we specify the directory to `Compilation.EmitLoc`, it will be
handled, allegedly, correctly.

Fixes #12858
@andrewrk andrewrk added the zig cc Zig as a drop-in C compiler feature label Sep 19, 2022
FabianHahn pushed a commit to FabianHahn/bazel-zig-cc that referenced this issue Sep 28, 2022
@motiejus
Revert "bump to zig 0.10.0-dev.3999+fda6d4477"
026d234 
This reverts commit f161caf.

This version has a bug that's been fixed upstream, but a new nightly did
not come out yet: ziglang/zig#12858
Vexu pushed a commit to Vexu/zig that referenced this issue Oct 10, 2022
@motiejus @Vexu
zig cc: emit to a.out if outpath is unspecified
d660030 
If `-o` is not specified for `zig cc` for linking, it should emit the
`a.out` (or equivalent) to the current directory. So then this:

    $ zig cc test.c

Should result in `./a.out`.

If directory is omitted from `Compilation.EmitLoc`, it will default to
the cache directory later in the compilation chain, which will result
in `a.out` missing in the current directory.

If we specify the directory to `Compilation.EmitLoc`, it will be
handled, allegedly, correctly.

Fixes ziglang#12858
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Labels
bug Observed behavior contradicts documented or intended behavior regression It worked in a previous version of Zig, but stopped working. zig cc Zig as a drop-in C compiler feature
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0.10.0
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zig cc: emit to a.out if outpath is unspecified motiejus/zig
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@andrewrk @motiejus @williamstein