-vvv annoyances

[dot-asm]

I think everybody would appreciate even verbose output to be on point. Here is typical output

[bar 0.1.0] OPT_LEVEL = Some(0)
[bar 0.1.0] TARGET = Some(x86_64-unknown-linux-gnu)
[bar 0.1.0] HOST = Some(x86_64-unknown-linux-gnu)
[bar 0.1.0] cargo:rerun-if-env-changed=CC_x86_64-unknown-linux-gnu
[bar 0.1.0] CC_x86_64-unknown-linux-gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=CC_x86_64_unknown_linux_gnu
[bar 0.1.0] CC_x86_64_unknown_linux_gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=HOST_CC
[bar 0.1.0] HOST_CC = None
[bar 0.1.0] cargo:rerun-if-env-changed=CC
[bar 0.1.0] CC = None
[bar 0.1.0] cargo:rerun-if-env-changed=CC_ENABLE_DEBUG_OUTPUT
[bar 0.1.0] RUSTC_WRAPPER = None
[bar 0.1.0] cargo:rerun-if-env-changed=CRATE_CC_NO_DEFAULTS
[bar 0.1.0] CRATE_CC_NO_DEFAULTS = None
[bar 0.1.0] DEBUG = Some(true)
[bar 0.1.0] CARGO_CFG_TARGET_FEATURE = Some(fxsr,sse,sse2)
[bar 0.1.0] cargo:rerun-if-env-changed=CFLAGS
[bar 0.1.0] CFLAGS = None
[bar 0.1.0] cargo:rerun-if-env-changed=HOST_CFLAGS
[bar 0.1.0] HOST_CFLAGS = None
[bar 0.1.0] cargo:rerun-if-env-changed=CFLAGS_x86_64_unknown_linux_gnu
[bar 0.1.0] CFLAGS_x86_64_unknown_linux_gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=CFLAGS_x86_64-unknown-linux-gnu
[bar 0.1.0] CFLAGS_x86_64-unknown-linux-gnu = None
[bar 0.1.0] CARGO_ENCODED_RUSTFLAGS = Some()
[bar 0.1.0] OUT_DIR = Some(/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out)
[bar 0.1.0] cargo:rerun-if-env-changed=CC_ENABLE_DEBUG_OUTPUT
[bar 0.1.0] cargo:rerun-if-env-changed=CRATE_CC_NO_DEFAULTS
[bar 0.1.0] CRATE_CC_NO_DEFAULTS = None
[bar 0.1.0] TARGET = Some(x86_64-unknown-linux-gnu)
[bar 0.1.0] CARGO_CFG_TARGET_FEATURE = Some(fxsr,sse,sse2)
[bar 0.1.0] HOST = Some(x86_64-unknown-linux-gnu)
[bar 0.1.0] cargo:rerun-if-env-changed=CFLAGS
[bar 0.1.0] CFLAGS = None
[bar 0.1.0] cargo:rerun-if-env-changed=HOST_CFLAGS
[bar 0.1.0] HOST_CFLAGS = None
[bar 0.1.0] cargo:rerun-if-env-changed=CFLAGS_x86_64_unknown_linux_gnu
[bar 0.1.0] CFLAGS_x86_64_unknown_linux_gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=CFLAGS_x86_64-unknown-linux-gnu
[bar 0.1.0] CFLAGS_x86_64-unknown-linux-gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=AR_x86_64-unknown-linux-gnu
[bar 0.1.0] AR_x86_64-unknown-linux-gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=AR_x86_64_unknown_linux_gnu
[bar 0.1.0] AR_x86_64_unknown_linux_gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=HOST_AR
[bar 0.1.0] HOST_AR = None
[bar 0.1.0] cargo:rerun-if-env-changed=AR
[bar 0.1.0] AR = None
[bar 0.1.0] cargo:rerun-if-env-changed=ARFLAGS
[bar 0.1.0] ARFLAGS = None
[bar 0.1.0] cargo:rerun-if-env-changed=HOST_ARFLAGS
[bar 0.1.0] HOST_ARFLAGS = None
[bar 0.1.0] cargo:rerun-if-env-changed=ARFLAGS_x86_64_unknown_linux_gnu
[bar 0.1.0] ARFLAGS_x86_64_unknown_linux_gnu = None
[bar 0.1.0] cargo:rerun-if-env-changed=ARFLAGS_x86_64-unknown-linux-gnu
[bar 0.1.0] ARFLAGS_x86_64-unknown-linux-gnu = None
[bar 0.1.0] cargo:rustc-link-lib=static=a
[bar 0.1.0] cargo:rustc-link-search=native=/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out

What are we to learn from 30-line repetition? Nothing. Originally the output at least included compiler command lines, which I for one found way more useful than above listing. But for some reason the command line exposure was made conditional on CC_ENABLE_DEBUG_OUTPUT environment variable. So let's consider the output with the variable set and without -vvv option first.

warning: bar@0.1.0: cc: error: unrecognized command-line option ‘-?’        
warning: bar@0.1.0: cc: fatal error: no input files
warning: bar@0.1.0: compilation terminated.

What are we to learn from this? Less than nothing. Because it's misleading by proclaiming "compilation terminated." More annoyingly we get this three lines for each flag_if_supported() invocation.

But let's move on to -vvv with one flag_is_supported(). Omitting the already mentioned lines we get

[bar 0.1.0] running: "cc" "-E" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/17730175534651035635detect_compiler_family.c"
[bar 0.1.0] # 0 "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/17730175534651035635detect_compiler_family.c"
[bar 0.1.0] # 0 "<built-in>"
[bar 0.1.0] # 0 "<command-line>"
[bar 0.1.0] # 1 "/usr/include/stdc-predef.h" 1 3 4
[bar 0.1.0] # 0 "<command-line>" 2
[bar 0.1.0] # 1 "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/17730175534651035635detect_compiler_family.c"
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] #pragma message "gcc"
[bar 0.1.0] 
[bar 0.1.0] running: "cc" "-?"
[bar 0.1.0] cargo:warning=cc: error: unrecognized command-line option '-?'
[bar 0.1.0] cargo:warning=cc: fatal error: no input files
[bar 0.1.0] cargo:warning=compilation terminated.
[bar 0.1.0] exit status: 1
[bar 0.1.0] running: "cc" "-E" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/6437633726814300714detect_compiler_family.c"
[bar 0.1.0] # 0 "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/6437633726814300714detect_compiler_family.c"
[bar 0.1.0] # 0 "<built-in>"
[bar 0.1.0] # 0 "<command-line>"
[bar 0.1.0] # 1 "/usr/include/stdc-predef.h" 1 3 4
[bar 0.1.0] # 0 "<command-line>" 2
[bar 0.1.0] # 1 "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/6437633726814300714detect_compiler_family.c"
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] 
[bar 0.1.0] #pragma message "gcc"
[bar 0.1.0] 
[bar 0.1.0] running: "cc" "-?"
[bar 0.1.0] cargo:warning=cc: error: unrecognized command-line option '-?'
[bar 0.1.0] cargo:warning=cc: fatal error: no input files
[bar 0.1.0] cargo:warning=compilation terminated.
[bar 0.1.0] exit status: 1
[bar 0.1.0] running: LC_ALL="C" "cc" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-4" "-fno-omit-frame-pointer" "-m64" "-Wall" "-Wextra" "-o" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/ea708c7824d36062-a.o" "-c" "src/a.c"
[bar 0.1.0] exit status: 0
[bar 0.1.0] running: LC_ALL="C" "cc" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-4" "-fno-omit-frame-pointer" "-m64" "-Wall" "-Wextra" "-o" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/ea708c7824d36062-b.o" "-c" "src/b.c"
[bar 0.1.0] exit status: 0
[bar 0.1.0] running: ZERO_AR_DATE="1" "ar" "cq" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/liba.a" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/ea708c7824d36062-a.o" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/ea708c7824d36062-b.o"
[bar 0.1.0] exit status: 0
[bar 0.1.0] running: "ar" "s" "/home/foo/bar/target/debug/build/bar-a3dff5830754fc93/out/liba.a"
[bar 0.1.0] exit status: 0

What do we learn from repetition? Nothing. What do we learn from the unique output? The very little we learn is effectively negated by the already mentioned misleading "compilation terminated" warning. And we're in total dark why there is duplication.

To summarize. The verbose output is excessively repetitive and appears to be self-serving, which diminishes its usefulness. Just in case for reference, "self-serving" refers the fact that the focus appears to be on providing debugging information for cc-rs maintainers as opposed to make it useful for cc-rs users.

[dot-asm]

A bonus annoyance. [To be fair you're not exactly in position to catch it, because it's uncommon.] Here is output from attempt to compile CUDA project I maintain on Windows without -vvv or CC_ENABLE_DEBUG_OUTPUT set:

warning: sppark@0.1.14: Compiler family detection failed since it does not define `__clang__`, `__GNUC__`, `__EMSCRIPTEN__` or `__VXWORKS__`, also does not accept cl style flag `-?`, fallback to treating it as GNU
warning: sppark@0.1.14: Compiler family detection failed due to error: ToolFamilyMacroNotFound: Expects macro `__clang__`, `__GNUC__` or `__EMSCRIPTEN__`, `__VXWORKS__` or accepts cl style flag `-?`, but found none
warning: sppark@0.1.14: Compiler family detection failed since it does not define `__clang__`, `__GNUC__`, `__EMSCRIPTEN__` or `__VXWORKS__`, also does not accept cl style flag `-?`, fallback to treating it as GNU
warning: sppark@0.1.14: Compiler family detection failed due to error: ToolFamilyMacroNotFound: Expects macro `__clang__`, `__GNUC__` or `__EMSCRIPTEN__`, `__VXWORKS__` or accepts cl style flag `-?`, but found none
warning: sppark@0.1.14: Compiler family detection failed since it does not define `__clang__`, `__GNUC__`, `__EMSCRIPTEN__` or `__VXWORKS__`, also does not accept cl style flag `-?`, fallback to treating it as GNU
warning: sppark@0.1.14: Compiler family detection failed due to error: ToolFamilyMacroNotFound: Expects macro `__clang__`, `__GNUC__` or `__EMSCRIPTEN__`, `__VXWORKS__` or accepts cl style flag `-?`, but found none
warning: sppark@0.1.14: Compiler family detection failed since it does not define `__clang__`, `__GNUC__`, `__EMSCRIPTEN__` or `__VXWORKS__`, also does not accept cl style flag `-?`, fallback to treating it as GNU
warning: sppark@0.1.14: Compiler family detection failed due to error: ToolFamilyMacroNotFound: Expects macro `__clang__`, `__GNUC__` or `__EMSCRIPTEN__`, `__VXWORKS__` or accepts cl style flag `-?`, but found none
warning: sppark@0.1.14: Compiler family detection failed since it does not define `__clang__`, `__GNUC__`, `__EMSCRIPTEN__` or `__VXWORKS__`, also does not accept cl style flag `-?`, fallback to treating it as GNU
warning: sppark@0.1.14: Compiler family detection failed due to error: ToolFamilyMacroNotFound: Expects macro `__clang__`, `__GNUC__` or `__EMSCRIPTEN__`, `__VXWORKS__` or accepts cl style flag `-?`, but found none

10 repetitions. For reference, nvcc is a "shapeshifter" compiler. It borrows host compiler to pre-process source code, but its command line is more reminiscent
of Unix command. The simplest solution would be to not probe if cuda flag is set and simply assume Unix syntax. Alternatively one can check if __NVCC__ macro is defined.

[NobodyXu]

That part is from the compiler detection bit though.

Maybe we could add some context to it?

[dot-asm]

The major point is usability of the verbose output. Being a crate maintainer that relies on cc-rs I a) don't want users to face unrelated and confusing warnings, let alone redundant ones; b) wish -vvv output was more useful to crate maintainers in case our users run into a problem and asked to provide the verbose output for troubleshooting. To give a concrete example of b). Certain .flag_if_supported was reported to not work on [ARM] MacOS with homebrew llvm-18. There is no way to discern the problem from the verbose output, be it with or without CC_ENABLE_DEBUG_OUTPUT set.

[NobodyXu]

Yeah maybe we should do something like log does then?

That's the best I can think of to reduce unwanted info