detect-tool-vendor-by-query

Detect tool vendor by query, not by name

When to use

You are writing code that branches on which compiler, linker, interpreter, or other build tool is in use — GCC vs. Clang, CPython vs. PyPy, BSD vs. GNU coreutils, system Python vs. a pyenv shim — and your current approach is to look at the executable's name or path ("gcc" in argv0, which python3, basename $CC).

Signal phrases: "we assume /usr/bin/gcc is GCC", "the driver is called cc so it must be…", "python3 on PATH is 3.x", or a bug report that reproduces only on macOS / only on a system with a vendor-renamed toolchain.

Problem

Tool names lie. Common traps:

• macOS ships /usr/bin/gcc but it's Apple Clang under the hood. Any substring check like 'gcc' in cc_path misclassifies it as GNU and then tries to pass GNU-only flags (-static-libgcc, -flto=auto, -fno-fat-lto-objects, …), which Clang rejects at link time.
• cc is a symlink whose target varies by distro: GCC on most Linux, Clang on FreeBSD / macOS, tcc on some minimal installs. The name cc tells you nothing.
• python3 on PATH may be the system's frozen 3.9, a pyenv shim, a Homebrew keg, or a virtualenv. Checking the path (/usr/bin/python3 → "system Python") gives you the source, not the version.
• GNU vs BSD coreutils — sed, awk, tar, date on macOS are BSD variants with different flag sets; they're spelled exactly the same as their GNU cousins.
• Cross-compilers and wrappers (ccache gcc, distcc clang, arm-linux-gnueabihf-gcc) contain the vendor substring but may forward to a different backend than the name implies.

The fix is always the same: ask the tool.

Solution

1. Run the tool's identity query once, at init time, and cache the result. Don't re-probe on every call site.
2. Parse a known-stable field, not the whole banner:
   • C/C++ drivers: first line of cc --version. Look for 'Apple clang' / 'clang' / 'gcc' / 'Free Software Foundation'. Normalize to a closed enum ({'clang', 'gcc', 'unknown'}).
   • Python: python -c 'import sys; print(sys.version_info[:2])' or python -V and parse "Python X.Y.Z". Compare as a tuple, never as a float (3.10 < 3.9 if you use floats).
   • coreutils: sed --version 2>&1 | head -1 → "GNU sed" vs. "invalid option" on BSD.
3. Have a defined unknown bucket. Exotic toolchains exist; don't let the detector crash on them. Emit a warning and fall back to the most conservative flag set.
4. Gate feature flags on the cached vendor, not on the path: