Flash C

A small C compiler and a full-screen, text-mode IDE for Linux.

• fcc is the command-line compiler. It reads C source and writes a native x86-64 Linux executable directly: no assembler, linker or C library is involved.
• fc is the IDE: pull-down menus, overlapping edit windows, an error Message window, option dialogs, a source-level debugger and hyper-linked online help, laid out like the classic DOS-era C IDEs.

Flash C compiles C (ANSI C89) with a few C99 conveniences. C++ is not supported.

Highlights

• Complete toolchain in one place. Editor, compiler, linker, run-time library, debugger and help are all part of the project.
• A real optimizer. 48 switchable optimizations: constant folding, global data-flow analysis, SSA, inlining, loop optimizations, register allocation, whole-program passes and profile-guided optimization. See Optimizations.
• Source-level debugger with breakpoints, watches, an expression evaluator and call stack.
• Per-function linking. Only the library functions your program uses end up in the executable.
• Classic diagnostics. Error hello.c 5: Undefined symbol 'x' in function main.
• Online help for the IDE, the language and every library function, with examples you can copy into the editor.

Quick start

Install a release (Linux x86-64): download flash-c-<version>-linux-x86_64.tar.gz from the Releases page, then

tar xzf flash-c-*.tar.gz
cd flash-c-*/
./install.sh              # installs to ~/.local; use --prefix DIR or run as root for /usr/local

./install.sh --uninstall removes it again. Installing is optional: the unpacked folder also runs in place with ./bin/fc and ./bin/fcc. See releasing for how releases are made.

Build from source: you need a C compiler (gcc or clang), make, and a terminal of at least 80×25 with UTF-8. 24-bit colour is used when COLORTERM=truecolor; otherwise 16 ANSI colours.

make                      # builds build/fc and build/fcc
./build/fc hello.c        # open (or create) hello.c in the IDE
./build/fcc hello.c       # or compile it directly; this produces ./hello
./hello

make test runs the whole test suite, and make install copies both programs and the help files to /usr/local.

In the IDE, type a program and press F2 to save, F9 to build and Ctrl+F9 to run it. If the build fails, the Message window lists the errors; press Enter on one to jump to the line. The user guide has the details.

A quick tour

Errors that take you to the line. The Message window lists errors and warnings; the cursor follows them with Alt+F7 and Alt+F8.

Menus and dialogs. Every command is in the menus, with a one-line hint on the status line. The Options dialogs hold the compiler, linker and environment settings.

Optimizations. Each optimization has its own check box, with a description on the status line. The Help button opens the matching help page.

Debugger. Set breakpoints with Ctrl+F8, step with F7 and F8, and watch values change.

Help. F1 opens the contents; Ctrl+F1 shows the topic for the word under the cursor, for example printf.

Documentation

Document	What is in it
User guide	Using the IDE: windows, menus, keys, the editor, projects, the debugger, online help.
Compiler reference	fcc switches, the language Flash C accepts, diagnostics, optimizations, profile-guided optimization, linking.
Library reference	Every header and function of the run-time library, with the module that implements it.
Architecture notes	How the compiler, optimizer, library, IDE and debugger work inside; for contributors.
Evidence	How the IDE structure was derived from a study of the reference IDE.

Project layout

src/compiler/   lexer and preprocessor, parser and type checker, optimizer, x86-64 code generator
                and ELF writer, compiler driver
src/ide/        terminal layer, windows, menus, dialogs, editor, help, debugger, commands
src/cli/        the fcc main program
runtime/        the run-time library in Flash C (lib/) and its headers (include/)
help/           the extended online help (*.fch), generated by tools/helpgen
tests/          compiler, diagnostics, optimizer, library, IDE and debugger tests
tools/          generators (library docs, help files, screenshots) and development helpers
docs/           the documentation, and the screenshots used in it
analysis/       the study of the reference IDE

Contributing

Bug reports and pull requests are welcome; see CONTRIBUTING.md for the workflow, code style and tests.

Tests

make test runs, in order: the compiler against gcc (tests/run.sh), the diagnostics text (diag.sh), the command-line switches (options.sh), each optimization (opt.sh) and a fuzz test that compiles random programs with and without optimization and compares their output (optfuzz.py), the help examples (helpexamples.py), the library (libtest.sh), and the IDE, projects and debugger driven through a pseudo-terminal (ide_smoke.py, project_smoke.py, debug_smoke.py).

The screenshots in this repository are made by the real IDE: run python3 tools/screenshots.py after a build to regenerate them.

Notice on the reference product

This project uses Turbo C (TC) only as a reference. It does not use any of its resources: no code, libraries, headers, help text or other files from it are included. All of the compiler code and the standard library source in this repository is original, generated code. The compiler and the IDE were developed by studying the executable binary of the Turbo C++ compiler, available at https://archive.org/details/turboc3.1_202112. The IDE structure (menu tables, dialog controls, status line, colour groups, compile, make and run behaviour) was derived from that study; the evidence and method are in analysis/EVIDENCE.md. The raw extraction output is not distributed with this repository.

License

Flash C is released under the MIT License.