Clang
LLVM's C/C++/Objective-C compiler frontend — Chris Lattner et al., 2007. Designed for better error messages and a more modular architecture than GCC.
Diagnostics focus: caret pointers at the exact position, "Did you mean…?" suggestions, targeted fix-its. Static Analyzer (deep code analysis) and Sanitizers (ASan, TSan, UBSan, MSan) built in. Powers Clang-tidy, clangd (LSP).
Default compiler on macOS, FreeBSD, Android NDK. Linux lets you choose GCC or Clang. Competitors: GCC (classic), MSVC (Windows-only), ICC (Intel, EOL).