Linking - TinyCC

After compilation, you typically need to link against libraries and add external symbols.

Adding libraries

tcc_add_library

Links a library to the compiled code. The library name follows the convention used by the -l linker option.

int tcc_add_library(TCCState *s, const char *libraryname);

TCCState*

required

The compilation context.

const char*

required

Library name without the “lib” prefix or file extension. For special cases, prefix with : to use an exact filename.

int

Returns 0 on success, -1 on error.

Example:

// Link with libm.so (math library)
tcc_add_library(s, "m");

// Link with libpthread.so
tcc_add_library(s, "pthread");

// Link with libcurl.so
tcc_add_library(s, "curl");

// Use exact filename (searches for "myexactlib.a")
tcc_add_library(s, ": myexactlib.a");

The function searches for libraries in this order:

Dynamic libraries (.so, .dylib, or .dll depending on platform)
Static libraries (.a)

tcc_add_library_path

Adds a directory to the library search path (equivalent to -L option).

int tcc_add_library_path(TCCState *s, const char *pathname);

TCCState*

required

The compilation context.

const char*

required

Directory path to add to the library search path.

int

Returns 0 on success.

Example:

// Add custom library paths
tcc_add_library_path(s, "/usr/local/lib");
tcc_add_library_path(s, "./build/lib");
tcc_add_library_path(s, "/opt/myapp/lib");

// Now libraries in these directories can be found
tcc_add_library(s, "mylib");  // Finds /usr/local/lib/libmylib.so

Adding symbols

tcc_add_symbol

Adds a symbol (function or variable) to the compiled program, making host application symbols available to compiled code.

int tcc_add_symbol(TCCState *s, const char *name, const void *val);

TCCState*

required

The compilation context.

const char*

required

Symbol name (must match the name used in compiled code).

const void*

required

Pointer to the function or variable.

int

Returns 0 on success, -1 on error.

Example:

// Function in host application
int host_add(int a, int b) {
    return a + b;
}

void host_log(const char *msg) {
    printf("[LOG] %s\n", msg);
}

// Make functions available to compiled code
tcc_add_symbol(s, "host_add", host_add);
tcc_add_symbol(s, "host_log", host_log);

// Now compile code that uses these functions
const char *code = 
    "extern int host_add(int, int);\n"
    "extern void host_log(const char*);\n"
    "\n"
    "int my_function() {\n"
    "    int result = host_add(10, 20);\n"
    "    host_log(\"Calculation done\");\n"
    "    return result;\n"
    "}\n";

tcc_compile_string(s, code);

// Global variable in host
const char config_path[] = "/etc/myapp.conf";
int max_connections = 100;

// Make variables available
tcc_add_symbol(s, "config_path", config_path);
tcc_add_symbol(s, "max_connections", &max_connections);

// Use in compiled code
const char *code = 
    "#include <stdio.h>\n"
    "extern const char config_path[];\n"
    "extern int max_connections;\n"
    "\n"
    "void show_config() {\n"
    "    printf(\"Config: %s\\n\", config_path);\n"
    "    printf(\"Max connections: %d\\n\", max_connections);\n"
    "}\n";

tcc_compile_string(s, code);

// Callback function in host
void on_event(const char *event, int value) {
    printf("Event: %s, Value: %d\n", event, value);
}

tcc_add_symbol(s, "on_event", on_event);

// Compiled code can call back
const char *code = 
    "extern void on_event(const char*, int);\n"
    "\n"
    "void process_data(int data) {\n"
    "    if (data > 100) {\n"
    "        on_event(\"threshold_exceeded\", data);\n"
    "    }\n"
    "}\n";

tcc_compile_string(s, code);

You must add symbols before calling tcc_relocate(). Symbols cannot be added after relocation.

Output file generation

tcc_output_file

Generates an output file (executable, library, or object). Do not call tcc_relocate() before this.

int tcc_output_file(TCCState *s, const char *filename);

TCCState*

required

The compilation context.

const char*

required

Path for the output file.

int

Returns 0 on success, -1 on error.

Example:

TCCState *s = tcc_new();
tcc_set_output_type(s, TCC_OUTPUT_EXE);

tcc_add_file(s, "main.c");
tcc_add_library(s, "m");

// Generate executable
if (tcc_output_file(s, "myprogram") < 0) {
    fprintf(stderr, "Failed to generate executable\n");
    return 1;
}

tcc_delete(s);

TCCState *s = tcc_new();
tcc_set_output_type(s, TCC_OUTPUT_DLL);

tcc_add_file(s, "mylib.c");

// Generate shared library
tcc_output_file(s, "libmylib.so");

tcc_delete(s);

TCCState *s = tcc_new();
tcc_set_output_type(s, TCC_OUTPUT_OBJ);

tcc_compile_string(s, 
    "int helper(int x) { return x * 2; }");

tcc_output_file(s, "helper.o");

tcc_delete(s);

Complete linking example

#include "libtcc.h"
#include <stdio.h>

// Host functions to expose
int add(int a, int b) {
    return a + b;
}

void log_message(const char *msg) {
    printf("[HOST] %s\n", msg);
}

// Host data
const char app_name[] = "MyApp";

int main() {
    TCCState *s;
    int (*compiled_main)(void);
    
    s = tcc_new();
    if (!s) return 1;
    
    tcc_set_output_type(s, TCC_OUTPUT_MEMORY);
    
    // Add library search paths
    tcc_add_library_path(s, "/usr/local/lib");
    tcc_add_library_path(s, "./lib");
    
    // Add system libraries
    tcc_add_library(s, "m");        // Math library
    tcc_add_library(s, "pthread");  // Threading
    
    // Add custom library
    tcc_add_library(s, "myutils");
    
    // Expose host symbols
    tcc_add_symbol(s, "add", add);
    tcc_add_symbol(s, "log_message", log_message);
    tcc_add_symbol(s, "app_name", app_name);
    
    // Compile code that uses everything
    const char *code =
        "#include <stdio.h>\n"
        "#include <math.h>\n"
        "\n"
        "extern int add(int, int);\n"
        "extern void log_message(const char*);\n"
        "extern const char app_name[];\n"
        "\n"
        "int main(void) {\n"
        "    printf(\"Running %s\\n\", app_name);\n"
        "    log_message(\"Starting calculation\");\n"
        "    \n"
        "    int result = add(5, 3);\n"
        "    double sq = sqrt(result);\n"
        "    \n"
        "    printf(\"Result: %d, sqrt: %f\\n\", result, sq);\n"
        "    log_message(\"Done\");\n"
        "    return 0;\n"
        "}\n";
    
    if (tcc_compile_string(s, code) < 0) {
        tcc_delete(s);
        return 1;
    }
    
    // Relocate before getting symbols
    if (tcc_relocate(s) < 0) {
        tcc_delete(s);
        return 1;
    }
    
    // Get and run the compiled main function
    compiled_main = tcc_get_symbol(s, "main");
    if (!compiled_main) {
        fprintf(stderr, "Could not find main\n");
        tcc_delete(s);
        return 1;
    }
    
    compiled_main();
    
    tcc_delete(s);
    return 0;
}

Platform-specific notes

Windows (PE format)

On Windows, dynamically linked data needs the dllimport attribute:

const char *code = 
    "#ifdef _WIN32\n"
    "__attribute__((dllimport))\n"
    "#endif\n"
    "extern const char config_path[];\n";

Library search order

Libraries are searched in this order:

Paths specified with tcc_add_library_path()
Default system paths (/usr/local/lib, /usr/lib, /lib)
Paths from LIBRARY_PATH environment variable

​Adding libraries

​tcc_add_library

​tcc_add_library_path

​Adding symbols

​tcc_add_symbol

​Output file generation

​tcc_output_file

​Complete linking example

​Platform-specific notes

​Windows (PE format)

​Library search order

Adding libraries

tcc_add_library

tcc_add_library_path

Adding symbols

tcc_add_symbol

Output file generation

tcc_output_file

Complete linking example

Platform-specific notes

Windows (PE format)

Library search order