`zig cc -MJ` (for `compile_commands.json`) does not work well with multiple files

[alexrp]

$ ls *.c
bar.c  foo.c  main.c
$ clang *.c -MJ o.json
$ cat o.json
{ "directory": "/home/alexrp/tests/c", "file": "bar.c", "output": "/tmp/bar-ebe0be.o", "arguments": ["/usr/lib/llvm-12/bin/clang", "-xc", "bar.c", "--target=x86_64-pc-linux-gnu"]},
{ "directory": "/home/alexrp/tests/c", "file": "foo.c", "output": "/tmp/foo-a01038.o", "arguments": ["/usr/lib/llvm-12/bin/clang", "-xc", "foo.c", "--target=x86_64-pc-linux-gnu"]},
{ "directory": "/home/alexrp/tests/c", "file": "main.c", "output": "/tmp/main-09a1d0.o", "arguments": ["/usr/lib/llvm-12/bin/clang", "-xc", "main.c", "--target=x86_64-pc-linux-gnu"]},
$ zig cc *.c -MJ o.json
$ cat o.json
{ "directory": "/home/alexrp/tests/c", "file": "bar.c", "output": "/home/alexrp/.cache/zig/tmp/14ea1c3c9c9678b9-bar.o", "arguments": ["/home/alexrp/zig/build/bin/zig", "-xc", "bar.c", "--target=x86_64-unknown-linux-gnu", "-nostdinc", "-fno-spell-checking", "-isystem", "/home/alexrp/zig/build/lib/zig/include", "-isystem", "/home/alexrp/zig/build/lib/zig/libc/include/x86_64-linux-gnu", "-isystem", "/home/alexrp/zig/build/lib/zig/libc/include/generic-glibc", "-isystem", "/home/alexrp/zig/build/lib/zig/libc/include/x86_64-linux-any", "-isystem", "/home/alexrp/zig/build/lib/zig/libc/include/any-linux-any", "-Xclang", "-target-cpu", "-Xclang", "skylake", "-Xclang", "-target-feature", "-Xclang", "-16bit-mode", "-Xclang", "-target-feature", "-Xclang", "-32bit-mode", "-Xclang", "-target-feature", "-Xclang", "-3dnow", "-Xclang", "-target-feature", "-Xclang", "-3dnowa", "-Xclang", "-target-feature", "-Xclang", "+64bit", "-Xclang", "-target-feature", "-Xclang", "+adx", "-Xclang", "-target-feature", "-Xclang", "+aes", "-Xclang", "-target-feature", "-Xclang", "-amx-bf16", "-Xclang", "-target-feature", "-Xclang", "-amx-int8", "-Xclang", "-target-feature", "-Xclang", "-amx-tile", "-Xclang", "-target-feature", "-Xclang", "+avx", "-Xclang", "-target-feature", "-Xclang", "+avx2", "-Xclang", "-target-feature", "-Xclang", "-avx512bf16", "-Xclang", "-target-feature", "-Xclang", "-avx512bitalg", "-Xclang", "-target-feature", "-Xclang", "-avx512bw", "-Xclang", "-target-feature", "-Xclang", "-avx512cd", "-Xclang", "-target-feature", "-Xclang", "-avx512dq", "-Xclang", "-target-feature", "-Xclang", "-avx512er", "-Xclang", "-target-feature", "-Xclang", "-avx512f", "-Xclang", "-target-feature", "-Xclang", "-avx512ifma", "-Xclang", "-target-feature", "-Xclang", "-avx512pf", "-Xclang", "-target-feature", "-Xclang", "-avx512vbmi", "-Xclang", "-target-feature", "-Xclang", "-avx512vbmi2", "-Xclang", "-target-feature", "-Xclang", "-avx512vl", "-Xclang", "-target-feature", "-Xclang", "-avx512vnni", "-Xclang", "-target-feature", "-Xclang", "-avx512vp2intersect", "-Xclang", "-target-feature", "-Xclang", "-avx512vpopcntdq", "-Xclang", "-target-feature", "-Xclang", "-avxvnni", "-Xclang", "-target-feature", "-Xclang", "+bmi", "-Xclang", "-target-feature", "-Xclang", "+bmi2", "-Xclang", "-target-feature", "-Xclang", "-branchfusion", "-Xclang", "-target-feature", "-Xclang", "-cldemote", "-Xclang", "-target-feature", "-Xclang", "+clflushopt", "-Xclang", "-target-feature", "-Xclang", "-clwb", "-Xclang", "-target-feature", "-Xclang", "-clzero", "-Xclang", "-target-feature", "-Xclang", "+cmov", "-Xclang", "-target-feature", "-Xclang", "+cx16", "-Xclang", "-target-feature", "-Xclang", "+cx8", "-Xclang", "-target-feature", "-Xclang", "-enqcmd", "-Xclang", "-target-feature", "-Xclang", "+ermsb", "-Xclang", "-target-feature", "-Xclang", "+f16c", "-Xclang", "-target-feature", "-Xclang", "-false-deps-lzcnt-tzcnt", "-Xclang", "-target-feature", "-Xclang", "+false-deps-popcnt", "-Xclang", "-target-feature", "-Xclang", "-fast-11bytenop", "-Xclang", "-target-feature", "-Xclang", "+fast-15bytenop", "-Xclang", "-target-feature", "-Xclang", "-fast-7bytenop", "-Xclang", "-target-feature", "-Xclang", "-fast-bextr", "-Xclang", "-target-feature", "-Xclang", "+fast-gather", "-Xclang", "-target-feature", "-Xclang", "-fast-hops", "-Xclang", "-target-feature", "-Xclang", "-fast-lzcnt", "-Xclang", "-target-feature", "-Xclang", "+fast-scalar-fsqrt", "-Xclang", "-target-feature", "-Xclang", "-fast-scalar-shift-masks", "-Xclang", "-target-feature", "-Xclang", "+fast-shld-rotate", "-Xclang", "-target-feature", "-Xclang", "+fast-variable-shuffle", "-Xclang", "-target-feature", "-Xclang", "+fast-vector-fsqrt", "-Xclang", "-target-feature", "-Xclang", "-fast-vector-shift-masks", "-Xclang", "-target-feature", "-Xclang", "+fma", "-Xclang", "-target-feature", "-Xclang", "-fma4", "-Xclang", "-target-feature", "-Xclang", "+fsgsbase", "-Xclang", "-target-feature", "-Xclang", "-fsrm", "-Xclang", "-target-feature", "-Xclang", "+fxsr", "-Xclang", "-target-feature", "-Xclang", "-gfni", "-Xclang", "-target-feature", "-Xclang", "-hreset", "-Xclang", "-target-feature", "-Xclang", "-idivl-to-divb", "-Xclang", "-target-feature", "-Xclang", "+idivq-to-divl", "-Xclang", "-target-feature", "-Xclang", "+invpcid", "-Xclang", "-target-feature", "-Xclang", "-kl", "-Xclang", "-target-feature", "-Xclang", "-lea-sp", "-Xclang", "-target-feature", "-Xclang", "-lea-uses-ag", "-Xclang", "-target-feature", "-Xclang", "-lvi-cfi", "-Xclang", "-target-feature", "-Xclang", "-lvi-load-hardening", "-Xclang", "-target-feature", "-Xclang", "-lwp", "-Xclang", "-target-feature", "-Xclang", "+lzcnt", "-Xclang", "-target-feature", "-Xclang", "+macrofusion", "-Xclang", "-target-feature", "-Xclang", "+mmx", "-Xclang", "-target-feature", "-Xclang", "+movbe", "-Xclang", "-target-feature", "-Xclang", "-movdir64b", "-Xclang", "-target-feature", "-Xclang", "-movdiri", "-Xclang", "-target-feature", "-Xclang", "-mwaitx", "-Xclang", "-target-feature", "-Xclang", "+nopl", "-Xclang", "-target-feature", "-Xclang", "-pad-short-functions", "-Xclang", "-target-feature", "-Xclang", "+pclmul", "-Xclang", "-target-feature", "-Xclang", "-pconfig", "-Xclang", "-target-feature", "-Xclang", "-pku", "-Xclang", "-target-feature", "-Xclang", "+popcnt", "-Xclang", "-target-feature", "-Xclang", "-prefer-128-bit", "-Xclang", "-target-feature", "-Xclang", "-prefer-256-bit", "-Xclang", "-target-feature", "-Xclang", "-prefer-mask-registers", "-Xclang", "-target-feature", "-Xclang", "-prefetchwt1", "-Xclang", "-target-feature", "-Xclang", "+prfchw", "-Xclang", "-target-feature", "-Xclang", "-ptwrite", "-Xclang", "-target-feature", "-Xclang", "-rdpid", "-Xclang", "-target-feature", "-Xclang", "+rdrnd", "-Xclang", "-target-feature", "-Xclang", "+rdseed", "-Xclang", "-target-feature", "-Xclang", "-retpoline", "-Xclang", "-target-feature", "-Xclang", "-retpoline-external-thunk", "-Xclang", "-target-feature", "-Xclang", "-retpoline-indirect-branches", "-Xclang", "-target-feature", "-Xclang", "-retpoline-indirect-calls", "-Xclang", "-target-feature", "-Xclang", "-rtm", "-Xclang", "-target-feature", "-Xclang", "+sahf", "-Xclang", "-target-feature", "-Xclang", "-serialize", "-Xclang", "-target-feature", "-Xclang", "-seses", "-Xclang", "-target-feature", "-Xclang", "-sgx", "-Xclang", "-target-feature", "-Xclang", "-sha", "-Xclang", "-target-feature", "-Xclang", "-shstk", "-Xclang", "-target-feature", "-Xclang", "+slow-3ops-lea", "-Xclang", "-target-feature", "-Xclang", "-slow-incdec", "-Xclang", "-target-feature", "-Xclang", "-slow-lea", "-Xclang", "-target-feature", "-Xclang", "-slow-pmaddwd", "-Xclang", "-target-feature", "-Xclang", "-slow-pmulld", "-Xclang", "-target-feature", "-Xclang", "-slow-shld", "-Xclang", "-target-feature", "-Xclang", "-slow-two-mem-ops", "-Xclang", "-target-feature", "-Xclang", "-slow-unaligned-mem-16", "-Xclang", "-target-feature", "-Xclang", "-slow-unaligned-mem-32", "-Xclang", "-target-feature", "-Xclang", "-soft-float", "-Xclang", "-target-feature", "-Xclang", "+sse", "-Xclang", "-target-feature", "-Xclang", "+sse2", "-Xclang", "-target-feature", "-Xclang", "+sse3", "-Xclang", "-target-feature", "-Xclang", "+sse4.1", "-Xclang", "-target-feature", "-Xclang", "+sse4.2", "-Xclang", "-target-feature", "-Xclang", "-sse4a", "-Xclang", "-target-feature", "-Xclang", "-sse-unaligned-mem", "-Xclang", "-target-feature", "-Xclang", "+ssse3", "-Xclang", "-target-feature", "-Xclang", "-tbm", "-Xclang", "-target-feature", "-Xclang", "-tsxldtrk", "-Xclang", "-target-feature", "-Xclang", "-uintr", "-Xclang", "-target-feature", "-Xclang", "-use-aa", "-Xclang", "-target-feature", "-Xclang", "-use-glm-div-sqrt-costs", "-Xclang", "-target-feature", "-Xclang", "-vaes", "-Xclang", "-target-feature", "-Xclang", "-vpclmulqdq", "-Xclang", "-target-feature", "-Xclang", "+vzeroupper", "-Xclang", "-target-feature", "-Xclang", "-waitpkg", "-Xclang", "-target-feature", "-Xclang", "-wbnoinvd", "-Xclang", "-target-feature", "-Xclang", "-widekl", "-Xclang", "-target-feature", "-Xclang", "+x87", "-Xclang", "-target-feature", "-Xclang", "-xop", "-Xclang", "-target-feature", "-Xclang", "+xsave", " "-Xclang", "-target-feature", "-Xclang", "+xsavec", "-Xclang", "-target-feature", "-Xclang", "+xsaveopt", "-Xclang", "-target-feature", "-Xclang", "+xsaves", "-fomit-frame-pointer", "-fsanitize=undefined", "-fsanitize-trap=undefined", "-mred-zone", "-D", "_DEBUG", "-Og", "-fstack-protector-strong", "--param", "ssp-buffer-size=4", "-fPIC", "-fno-unwind-tables", "-isystem", "/usr/local/include", "-isystem", "/usr/include/x86_64-linux-gnu", "-isystem", "/usr/include", "-c", "-o", "/home/alexrp/.cache/zig/tmp/abd94befe6eeb02-main.o", "--target=x86_64-unknown-linux-gnu"]},

Note how only one file entry is emitted by Zig.

[alexrp]

For anyone else running into this and looking for a workaround, -gen-cdb-fragment-path cdb will cause Clang to output JSON fragment files to the cdb directory that you can then stitch together to form a complete compilation database. This comes with the caveat that you have to clear both that directory and the Zig cache directory completely when compiler flags change or .c/.cxx files are added/removed.

[g-berthiaume]

+1 for this feature. That would be very helpful to integrate zig with other parts of the C ecosystem. For example, using clang-tidy.

[VisenDev]

+1

[mundusnine]

+1

[VisenDev]

I would add that this LSP integration issue is the main reason keeping me from integrating into my existing C projects

It would really be nice to have clangd or some other LSP work with zig built C projects

[neurocyte]

I have builds produce a working compile_commands.json for my zig-built-cpp projects. I do this:

• Add "-gen-cdb-fragment-path", ".cache/cdb" to my addCSourceFiles flags (make sure you don't have -MJ too)
• Run (echo \[ ; cat .cache/cdb/* ; echo {}\]) | perl -0777 -pe 's/,\n\{\}//igs' | jq . | grep -v 'no-default-config' > compile_commands.json (or something similar) after each build

I guess this could be better integrated into Zig's build system, but it works just fine for me without any special support from zig.

[kassane]

Recently a user made a compile_commands.json generator which may help this issue. https://github.com/the-argus/raylib-chipmunk-crossplatform-template/blob/main/build/compile_commands.zig

[the-argus]

@kassane i have no clue how you found and noticed my little repo but thank you :)

I have refined and packaged that functionality for easy use with zig v0.11.0 now: https://github.com/the-argus/zig-compile-commands

It doesn't know anything about what zig cc commands actually get executed, so it's more of a mimicry of what the zig compiler is actually doing in order to put enough into compile_commands to satisfy clangd specifically for my project. Currently it doesn't support config headers and I'm sure there will be other holes to patch.

[thezealousfool]

+1

[jonathanmarvens]

Hey, please check out my PR for this feature: #18391. We can continue the discussion there.

Update: @alexrp pointed out in a comment that #18391 doesn't actually address this particular issue. #18391 covers the zig build use case while this issue is focused on zig cc which has to do with the Clang driver.