C .gitignore template

The compilation pipeline leaves a trail at every stage and this template follows it. *.o and *.obj are the object files produced from each translation unit before linking, one per source file, and they are the single largest source of churn in a C repository that forgets to ignore them. *.gch and *.pch are precompiled headers, an optimisation that is entirely local to one build configuration.

The library rules cover both halves of the linking story. *.a and *.lib are static archives, *.so, *.so.* and *.dylib are shared objects on Unix, macOS and their variants, and *.dll is the Windows equivalent. *.la and *.lo come from libtool. All of these are outputs, but they are also exactly the file types you might legitimately vendor as a prebuilt third party dependency, so check before assuming the rule is harmless.

Executables are covered by *.exe, *.out and *.app. On Linux and macOS a compiled binary often has no extension at all, so the same gap that affects other compiled languages applies here: a binary named after your project will not be matched unless you add a rule or build into an ignored directory.

The debug symbol rules are platform specific. *.pdb and *.idb are the Windows symbol database and its intermediate form. *.dSYM/ is the macOS symbol bundle, which is a directory rather than a file and can easily be larger than the binary it describes. *.elf and *.ilk cover embedded output and incremental linker state.

Two rules deserve a second look. *.map is a linker map file listing symbol addresses, but the same extension is used by source maps in a repository that also contains web assets. *.su is a stack usage file from the compiler, harmless but obscure enough that people delete the line without knowing what it was.