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Overview

The mcc command compiles C source files through a complete compilation pipeline: preprocessing, parsing, lowering to Three Address Code (TACKY), code generation, and assembly/linking.

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Basic Usage

mcc [OPTIONS] <INPUT>

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Arguments

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INPUT
path
required
The C source file to compile

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Options

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--output
path
The output file path for the compiled binary. If not specified, defaults to the input filename without extension.Short form: -oExample:
mcc -o myprogram main.c
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--target
triple
The target triple for cross-compilation (e.g., x86_64-unknown-linux-gnu). Defaults to the host system’s target.Default: Host system targetExample:
mcc --target x86_64-unknown-linux-gnu main.c
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--color
choice
Control colored output for diagnostics.Choices: auto, always, neverDefault: autoExample:
mcc --color always main.c

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Examples

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Compile a Simple Program

mcc hello.c
This compiles hello.c and produces an executable named hello in the current directory. Input: hello.c 
int main(void) {
    return 42;
}
Output: 
$ mcc hello.c
$ ./hello
$ echo $?
42

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Specify Output File

mcc -o myprogram main.c
Compiles main.c and writes the executable to myprogram.

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Cross-Compilation

mcc --target x86_64-unknown-linux-gnu main.c
Compiles for a specific target architecture.

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Disable Colored Output

mcc --color never main.c
Useful for CI/CD pipelines or when redirecting output to files.

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Compilation Pipeline

The mcc compiler executes the following stages:
  1. Preprocessing - Expands macros and includes (delegates to system C preprocessor)
  2. Lexing - Tokenizes the preprocessed source
  3. Parsing - Builds an Abstract Syntax Tree (AST)
  4. Validation - Type checking and semantic analysis
  5. Lowering - Converts AST to Three Address Code (TACKY IR)
  6. Code Generation - Generates assembly instructions
  7. Assembly - Produces object files and links into executable
You can stop at any stage using the stage-specific flags. See Stage Control for details.

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Diagnostics

The compiler emits diagnostics with severity levels:
  • Error - Compilation cannot continue
  • Warning - Potential issues that don’t prevent compilation
  • Note - Additional context for other diagnostics
Diagnostics include source location information with line numbers and column markers: 
$ mcc invalid.c
error: expected ';' after return statement
  --> invalid.c:2:5
   |
 2 |     return 42
   |              ^ expected ';'

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Exit Codes

  • 0 - Compilation succeeded
  • Non-zero - Compilation failed (syntax error, type error, or system error)

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Environment Variables

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CC
string
The C compiler to use for preprocessing and linking. Defaults to cc.Default: ccExample:
CC=gcc mcc main.c
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RUST_LOG
string
Controls tracing output for debugging the compiler itself.Default: warn,mcc=debug,mcc-syntax=debug,mcc-driver=debugExample:
RUST_LOG=trace mcc main.c

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