when passing -### ("dry_run") avoid actually running compilation and linking child processes

[andrewrk]

zig/src/main.zig

Lines 1072 to 1076 in 8eaaa90

	.dry_run => {
	verbose_link = true;
	try clang_argv.append("-###");
	// XXX: Don't execute anything!
	},

Follow-up to #7166

[FireFox317]

Ah that is probably why the configure step in CMake is so slow.

[motiejus]

This is a problem for Golang, as it runs -### to understand some things about the compiler:

Zig today:

$ zig cc -### -x c - 
-:1:1: error: unable to build C object: FileNotFound

clang-16 today:

$ clang-16 -### -x c - 
Ubuntu clang version 16.0.1 (++20230328073357+42d1b276f779-1~exp1~20230328073502.65)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
 "/usr/lib/llvm-16/bin/clang" "-cc1" "-triple" "x86_64-pc-linux-gnu" "-emit-obj" "-mrelax-all" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "-" "-mrelocation-model" "pic" "-pic-level" "2" "-pic-is-pie" "-mframe-pointer=all" "-fmath-errno" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-funwind-tables=2" "-target-cpu" "x86-64" "-tune-cpu" "generic" "-mllvm" "-treat-scalable-fixed-error-as-warning" "-debugger-tuning=gdb" "-fcoverage-compilation-dir=/code/zig/build" "-resource-dir" "/usr/lib/llvm-16/lib/clang/16" "-internal-isystem" "/usr/lib/llvm-16/lib/clang/16/include" "-internal-isystem" "/usr/local/include" "-internal-isystem" "/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include" "-internal-externc-isystem" "/usr/include/x86_64-linux-gnu" "-internal-externc-isystem" "/include" "-internal-externc-isystem" "/usr/include" "-fdebug-compilation-dir=/code/zig/build" "-ferror-limit" "19" "-fgnuc-version=4.2.1" "-fcolor-diagnostics" "-faddrsig" "-D__GCC_HAVE_DWARF2_CFI_ASM=1" "-o" "/tmp/--55cca3.o" "-x" "c" "-"
 "/usr/bin/ld" "-pie" "-z" "relro" "--hash-style=gnu" "--build-id" "--eh-frame-hdr" "-m" "elf_x86_64" "-dynamic-linker" "/lib64/ld-linux-x86-64.so.2" "-o" "a.out" "/lib/x86_64-linux-gnu/Scrt1.o" "/lib/x86_64-linux-gnu/crti.o" "/usr/bin/../lib/gcc/x86_64-linux-gnu/11/crtbeginS.o" "-L/usr/bin/../lib/gcc/x86_64-linux-gnu/11" "-L/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../lib64" "-L/lib/x86_64-linux-gnu" "-L/lib/../lib64" "-L/usr/lib/x86_64-linux-gnu" "-L/usr/lib/../lib64" "-L/usr/lib/llvm-16/bin/../lib" "-L/lib" "-L/usr/lib" "/tmp/--55cca3.o" "-lgcc" "--as-needed" "-lgcc_s" "--no-as-needed" "-lc" "-lgcc" "--as-needed" "-lgcc_s" "--no-as-needed" "/usr/bin/../lib/gcc/x86_64-linux-gnu/11/crtendS.o" "/lib/x86_64-linux-gnu/crtn.o"

zig with #14462 : better, but still not compatible:

$ echo  | stage4/bin/zig cc -### -x c - 
Ubuntu clang version 16.0.1 (++20230328073357+42d1b276f779-1~exp1~20230328073502.65)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /code/zig/build
 (in-process)
 "/code/zig/build/stage4/bin/zig" "-cc1" "-triple" "x86_64-unknown-linux-gnu" "-emit-obj" "-mrelax-all" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "11b2af1f83bd4f4f-stdin.c" "-mrelocation-model" "pic" "-pic-level" "2" "-fhalf-no-semantic-interposition" "-mframe-pointer=all" "-fmath-errno" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-funwind-tables=2" "-target-cpu" "x86-64" "-tune-cpu" "generic" "-mllvm" "-treat-scalable-fixed-error-as-warning" "-debug-info-kind=constructor" "-dwarf-version=4" "-debugger-tuning=gdb" "-fcoverage-compilation-dir=/code/zig/build" "-nostdsysteminc" "-nobuiltininc" "-resource-dir" "/code/zig/build/stage4/lib/clang/16" "-dependency-file" "/home/motiejus/.cache/zig/tmp/31c071f0ffbd175a-11b2af1f83bd4f4f-stdin.o.d" "-MT" "/home/motiejus/.cache/zig/tmp/31c071f0ffbd175a-11b2af1f83bd4f4f-stdin.o" "-sys-header-deps" "-MV" "-isystem" "/code/zig/lib/include" "-isystem" "/usr/include" "-isystem" "/usr/include/x86_64-linux-gnu" "-isystem" "/usr/local/include" "-isystem" "/usr/include/x86_64-linux-gnu" "-isystem" "/usr/include" "-D" "__GLIBC_MINOR__=35" "-D" "_DEBUG" "-O0" "-fdebug-compilation-dir=/code/zig/build" "-ferror-limit" "19" "-fsanitize=alignment,array-bounds,bool,builtin,enum,float-cast-overflow,function,integer-divide-by-zero,nonnull-attribute,null,pointer-overflow,return,returns-nonnull-attribute,shift-base,shift-exponent,signed-integer-overflow,unreachable,vla-bound" "-fsanitize-trap=alignment,array-bounds,bool,builtin,enum,float-cast-overflow,function,integer-divide-by-zero,nonnull-attribute,null,pointer-overflow,return,returns-nonnull-attribute,shift-base,shift-exponent,signed-integer-overflow,unreachable,vla-bound" "-fno-sanitize-memory-param-retval" "-fno-sanitize-address-use-odr-indicator" "-stack-protector" "2" "-stack-protector-buffer-size" "4" "-fgnuc-version=4.2.1" "-fcolor-diagnostics" "-fno-spell-checking" "-target-cpu" "skylake" "-target-feature" "-16bit-mode" "-target-feature" "-32bit-mode" "-target-feature" "-3dnow" "-target-feature" "-3dnowa" "-target-feature" "+64bit" "-target-feature" "+adx" "-target-feature" "+aes" "-target-feature" "+allow-light-256-bit" "-target-feature" "-amx-bf16" "-target-feature" "-amx-fp16" "-target-feature" "-amx-int8" "-target-feature" "-amx-tile" "-target-feature" "+avx" "-target-feature" "+avx2" "-target-feature" "-avx512bf16" "-target-feature" "-avx512bitalg" "-target-feature" "-avx512bw" "-target-feature" "-avx512cd" "-target-feature" "-avx512dq" "-target-feature" "-avx512er" "-target-feature" "-avx512f" "-target-feature" "-avx512fp16" "-target-feature" "-avx512ifma" "-target-feature" "-avx512pf" "-target-feature" "-avx512vbmi" "-target-feature" "-avx512vbmi2" "-target-feature" "-avx512vl" "-target-feature" "-avx512vnni" "-target-feature" "-avx512vp2intersec
t" "-target-feature" "-avx512vpopcntdq" "-target-feature" "-avxifma" "-target-feature" "-avxneconvert" "-target-feature" "-avxvnni" "-target-feature" "-avxvnniint8" "-target-feature" "+bmi" "-target-feature" "+bmi2" "-target-feature" "-branchfusion" "-target-feature" "-cldemote" "-target-feature" "+clflushopt" "-targe
t-feature" "-clwb" "-target-feature" "-clzero" "-target-feature" "+cmov" "-target-feature" "-cmpccxadd" "-target-feature" "+crc32" "-target-feature" "+cx16" "-target-feature" "+cx8" "-target-feature" "-enqcmd" "-target-feature" "+ermsb" "-target-feature" "+f16c" "-target-feature" "-false-deps-getmant" "-target-feature" "-false-deps-lzcnt-tzcnt" "-target-feature" "-false-deps-mulc" "-target-feature" "-false-deps-mullq" "-target-feature" "-false-deps-perm" "-target-feature" "+false-deps-popcnt" "-target-feature" "-false-deps-range" "-target-feature" "-fast-11bytenop" "-target-feature" "+fast-15bytenop" "-target-feature" "-fast-7bytenop" "-target-feature" "-fast-bextr" "-target-feature" "+fast-gather" "-target-feature" "-fast-hops" "-target-feature" "-fast-lzcnt" "-target-feature" "-fast-movbe" "-target-feature" "+fast-scalar-fsqrt" "-target-feature" "-fast-scalar-shift-masks" "-target-feature" "+fast-shld-rotate" "-target-feature" "+fast-variable-crosslane-shuffle" "-target-feature" "+fast-variable-perlane-shuffle" "-target-feature" "+fast-vector-fsqrt" "-target-feature" "-fast-vector-shift-masks" "-target-feature" "+fma" "-target-feature" "-fma4" "-target-feature" "+fsgsbase" "-target-feature" "-fsrm" "-target-feature" "+fxsr" "-target-feature" "-gfni" "-target-feature" "-harden-sls-ijmp" "-target-feature" "-harden-sls-ret" "-target-feature" "-hreset" "-target-feature" "-idivl-to-divb" "-target-feature" "+idivq-to-divl" "-target-feature" "+invpcid" "-target-feature" "-kl" "-target-feature" "-lea-sp" "-target-feature" "-lea-uses-ag" "-target-feature" "-lvi-cfi" "-target-feature" "-lvi-load-hardening" "-target-feature" "-lwp" "-target-feature" "+lzcnt" "-target-feature" "+macrofusion" "-target-feature" "+mmx" "-target-feature" "+movbe" "-target-feature" "-movdir64b" "-target-feature" "-movdiri" "-target-feature" "-mwaitx" "-target-feature" "+nopl" "-target-feature" "-pad-short-functions" "-target-feature" "+pclmul" "-target-feature" "-pconfig" "-target-feature" "-pku" "-target-feature" "+popcnt" "-target-feature" "-prefer-128-bit" "-target-feature" "-prefer-256-bit" "-target-feature" "-prefer-mask-registers" "-target-feature" "-prefetchi" "-target-feature" "-prefetchwt1" "-target-feature" "+prfchw
" "-target-feature" "-ptwrite" "-target-feature" "-raoint" "-target-feature" "-rdpid" "-target-feature" "-rdpru" "-target-feature" "+rdrnd" "-target-feature" "+rdseed" "-target-feature" "-retpoline" "-target-feature" "-retpoline-external-thunk" "-target-feature" "-retpoline-indirect-branches" "-target-feature" "-retpoline-indirect-calls" "-target-feature" "+rtm" "-target-feature" "+sahf" "-target-feature" "-sbb-dep-breaking" "-target-feature" "-serialize" "-target-feature" "-seses" "-target-feature" "+sgx" "-target-feature" "-sha" "-target-feature" "-shstk" "-target-feature" "+slow-3ops-lea" "-target-feature" "-slow-incdec" "-target-feature" "-slow-lea" "-target-feature" "-slow-pmaddwd" "-target-feature" "-slow-pmulld" "-target-feature" "-slow-shld" "-target-feature" "-slow-two-mem-ops" "-target-feature" "-slow-unaligned-mem-16" "-target-feature" "-slow-unaligned-mem-32" "-target-feature" "-soft-float" "-target-feature" "+sse" "-target-feature" "+sse2" "-target-feature" "+sse3" "-target-feature" "+sse4.1" "-target-feature" "+sse4.2" "-target-feature" "-sse4a" "-target-feature" "-sse-unaligned-mem" "-target-feature" "+ssse3" "-target-feature" "-tagged-globals" "-target-feature" "-tbm" "-target-feature" "-tsxldtrk" "-target-feature" "-uintr" "-target-feature" "-use-glm-div-sqrt-costs" "-target-feature" "-use-slm-arith-costs" "-target-feature" "-vaes" "-target-feature" "-vpclmulqdq" "-target-feature" "+vzeroupper" "-target-feature" "-waitpkg" "-target-feature" "-wbnoinvd" "-target-feature" "-widekl" "-target-feature" "+x87" "-target-feature" "-xop" "-target-feature" "+xsave" "-target-feature" "+xsavec" "-target-feature" "+xsaveopt" "-target-feature" "+xsaves" "-faddrsig" "-D__GCC_HAVE_DWARF2_CFI_ASM=1" "-o" "/home/motiejus/.cache/zig/tmp/31c071f0ffbd175a-11b2af1f83bd4f4f-stdin.o" "-x" "c" "/home/motiejus/.cache/zig/tmp/11b2af1f83bd4f4f-stdin.c"
/home/motiejus/.cache/zig/tmp/11b2af1f83bd4f4f-stdin.c:1:1: error: unable to build C object: FileNotFound

[andrewrk]

Still a problem when -c is not used. See discussion here: #15738 (comment)