Overview

Introduction to the libtcc library for dynamic C code generation

The libtcc library enables you to use TCC as a backend for dynamic code generation. It allows you to compile C code at runtime and execute it directly in memory.

Key features

• In-memory compilation: Compile C source code to executable code in memory without generating intermediate files
• Symbol management: Add and retrieve symbols (functions and variables) dynamically
• Fast compilation: Leverage TCC’s extremely fast compilation speed
• Flexible output: Generate executables, shared libraries, object files, or run code directly in memory
• Error handling: Custom error and warning callbacks for integration into your application

Basic workflow

Using libtcc follows a simple pattern:

1. Initialize: Create a new compilation context with tcc_new()
2. Configure: Set output type, include paths, and compiler options
3. Compile: Add C source code using tcc_compile_string() or tcc_add_file()
4. Link: Add libraries and symbols with tcc_add_library() and tcc_add_symbol()
5. Execute: Either run code in memory or output to a file
6. Cleanup: Free resources with tcc_delete()

Quick example

#include "libtcc.h"

int main() {
    TCCState *s;
    int (*func)(int);
    
    // Create compilation context
    s = tcc_new();
    if (!s) return 1;
    
    // Set output type to memory
    tcc_set_output_type(s, TCC_OUTPUT_MEMORY);
    
    // Compile C code
    tcc_compile_string(s, 
        "int add(int a, int b) { return a + b; }");
    
    // Relocate code
    if (tcc_relocate(s) < 0) return 1;
    
    // Get function pointer
    func = tcc_get_symbol(s, "add");
    
    // Call the compiled function
    int result = func(5, 3);  // Returns 8
    
    // Cleanup
    tcc_delete(s);
    return 0;
}

Output types

libtcc supports multiple output types, set via tcc_set_output_type():

• TCC_OUTPUT_MEMORY: Compile and run code in memory (default for dynamic generation)
• TCC_OUTPUT_EXE: Generate an executable file
• TCC_OUTPUT_DLL: Generate a dynamic library
• TCC_OUTPUT_OBJ: Generate an object file
• TCC_OUTPUT_PREPROCESS: Only preprocess the source code

Thread safety

The global TCC state is protected by semaphores for basic thread safety, but you should generally avoid using the same TCCState from multiple threads simultaneously. Create separate TCCState instances for concurrent compilation.

Custom memory allocation

You can provide a custom memory allocator using tcc_set_realloc() before creating any TCCState instances. This affects all memory allocation performed by TCC.

Error handling

By default, errors and warnings are printed to stderr. You can set a custom error handler with tcc_set_error_func() to integrate TCC’s diagnostics into your application’s logging or UI.

Next steps

• Initialization - Learn how to create and configure a TCC compilation context
• Compilation - Compile C source code from strings or files
• Linking - Link libraries and manage dependencies
• Execution - Run compiled code or generate output files
• Symbols - Work with symbols and function pointers