tinycc/AGENTS.md

TinyCC (Tiny C Compiler)

Build & Test

./configure && make && make test

• make builds tcc + libtcc.a + libtcc1.a. libtcc1.a is built by a recursive make -C lib.
• make test runs the full test suite (tests/), ~2 minutes.
• Run a single tests2 test: make tests2.37 (run) or make tests2.37+ (update .expect).
• Run a single tests/pp test: make testspp.17.
• Sanitizer tests: make sani-test, make sani-tests2.37, make sani-testspp.17.
• Coverage tests: make tcov-test, make tcov-tests2.37, make tcov-testspp.17.
• Test installed tcc: make test-install.

Architecture

• Single-file-ish compiler: tcc compiles itself (or can be bootstrapped). tcc.c is the main entrypoint; tccpp.c handles preprocessing, tccgen.c handles code generation, tccelf.c handles ELF linking, tccasm.c handles inline asm, tccrun.c handles runtime execution, tccdbg.c handles debug info.
• Backend files per architecture: i386-gen.c, x86_64-gen.c, arm-gen.c, arm64-gen.c, riscv64-gen.c, c67-gen.c, plus corresponding asm/link files.
• Generated file: include/tccdefs.h is converted to tccdefs_.h by c2str.exe (built from conftest.c). Always exists after first make.
• Cross-compilers: make cross builds all cross-compilers; make cross-i386, make cross-x86_64, etc. for one target. make CROSS_TARGET=i386 ONE_SOURCE=yes for single-object cross build.
• ONE_SOURCE=yes: builds tcc as a single object file (default for cross-compilers, native uses separate objects).

Coding Style

• C90 with these pre-existing non-C90 features: long long, inline, // comments, unnamed struct/union fields, empty macro arguments, assignment between function pointer and void *.
• Indentation: 4 spaces for most files; some files (e.g. i386-gen.c) use 2 spaces for deep nesting.
• Do not reformat existing code unless the change is the primary purpose.
• Remove tabs and trailing whitespace from modified lines.
• Check with ./configure --extra-cflags="-std=c90 -Wpedantic".

Test Quirks

• test.ref (reference output) is generated from tcctest.c using gcc: (cd tests && gcc -I.. tcctest.c && valgrind -q ./a.out > test.ref) then make test TCC="valgrind -q --leak-check=full $(pwd)/tcc -B$(pwd) -I$(pwd)".
• VLA tests (79_vla_continue) produce expected invalid reads under Valgrind.
• tests2 skip list is in tests/tests2/Makefile (architecture- and config-specific skips).
• Some tests need special flags (see FLAGS = assignments in tests/tests2/Makefile).
• Bound-check tests (-b flag) are skipped when CONFIG_bcheck=no.
• .expect files are generated with gcc by default; some use TCC (flagged with GEN-TCC).

Language Extension: Optional Semicolons

Semicolons are optional after most statements and declarations:

• return, break, continue, goto, expression statements
• do-while trailing semicolon
• Variable declarations

Semicolons are still required for:

• for() loop init/condition/increment sections (e.g., for(i=0; i<n; i++))
• Old-style function parameter declarations
• Struct/enum member declarations

The skip(';') function in tccpp.c:100 errors if token doesn't match. Use if (tok == ';') next(); instead to make semicolons optional.