C Threads

A C library combining multiple packages for cross-platform development:

• custom malloc with rpmalloc.
• emulated C11 thread using Pthreads, or Pthreads4w.
• emulated C11 Atomic with c-atomic.
• general Linux compatibility headers for Windows, including a mmap compilation.

The deps folder has Windows build/fork of pthread-win32.

This library is a minimal, portable implementation of basic threading and atomics for C. They closely mimic the functionality and naming of the standard C11 Thread, and C11 Atomic, should be easily replaceable with the corresponding standard variants.

Custom malloc is a fork rpmalloc has no dependency on thread_local and can be compiled using Tiny C compiler. All malloc operations are lockless, and implements a emulated Thread-local storage via macro tls_storage(type, variable) as:

example.h

#include <cthreads.h>
#include <rpmalloc.h>
#include <stdio.h>
#include <assert.h>
tls_storage_extern(int, gLocalVar);

example.c

#include "example.h"
#define THREAD_COUNT 5

tls_storage(int, gLocalVar)

static int thread_local_storage(void *aArg) {
    int thread = *(int *)aArg;
    free(aArg);

    int data = thread + rand();
    *gLocalVar() = data;
    usleep(10);
    printf("thread #%d, gLocalVar is: %d\n", thread, *gLocalVar());
    assert(*gLocalVar() == data);
    return 0;
}

void emulated_tls(void) {
    thrd_t t[THREAD_COUNT];
    *gLocalVar() = 1;

    for (int i = 0; i < THREAD_COUNT; i++) {
        int *n = malloc(sizeof * n);
        *n = i;
        thrd_create(t + i, thread_local_storage, n);
    }

    for (int i = 0; i < THREAD_COUNT; i++) {
        thrd_join(t[i], NULL);
    }

    assert(*gLocalVar() == 1);
}

int main(void) {
    emulated_tls();
    return 0;
}

cthreads.h implements thrd_local(type, variable) macro, same behavior as above, but will not emulate if feature is available in your compiler, should be used for cross compatibility calling.

Emulate/create/control Thread Local Storage via macros

The design of these macros follow normal behaviors when using thread local storage.

In rpmalloc.h

The macro tls_storage_extern(type, variable) make function proto, and macro tls_storage(type, variable) will create functions as:

C_API int rpmalloc_variable_tls;
C_API tls_storage_t rpmalloc_variable_tss;
C_API type* variable(void);
C_API void variable_delete(void);

The macro tls_storage(type, variable) will create the functions using:

C_API int rpmalloc_tls_create(tls_storage_t *key, tls_dtor_t dtor);
C_API void rpmalloc_tls_delete(tls_storage_t key);
C_API void *rpmalloc_tls_get(tls_storage_t key);
C_API int rpmalloc_tls_set(tls_storage_t key, void *val);

In cthreads.h

The macro thrd_local_extern(type, variable) make functions proto, and thrd_local(type, variable) create functions as:

If compiler support native thread_local.

C_API thread_local type* thrd_variable_tls;
C_API void variable_del(void);
C_API void variable_update(type* value);
C_API bool is_variable_empty(void);
C_API type* variable(void);

Macro thrd_local(type, variable) also add.

static thread_local type thrd_variable_buffer;

If emulating thread_local is detected/required, will use platform thread library routines.

C_API int thrd_variable_tls;
C_API tss_t thrd_variable_tss;
C_API void variable_del(void);
C_API void variable_update(type* value);
C_API bool is_variable_empty(void);
C_API type* variable(void);

Macro thrd_local(type, variable) also add when emulating.

static type thrd_variable_buffer;

• The macro thrd_local_external(type, variable) makes non-pointer version of above.
• The macro thrd_static(type, variable) makes local non-extern static function version of above.

Installation

Any commit with an tag is considered stable for release at that version point.

If there are no binary available for your platform under Releases then build using cmake, which produces static libraries by default.

You will need the binary stored under built, and *.h headers, or complete include folder if Windows.

Linux

mkdir build
cd build
cmake .. -DCMAKE_BUILD_TYPE=Debug/Release -D BUILD_TESTS=OFF -D BUILD_EXAMPLES=OFF # use to not build tests and examples
cmake --build .

Windows

mkdir build
cd build
cmake .. -D BUILD_TESTS=OFF -D BUILD_EXAMPLES=OFF # use to not build tests and examples
cmake --build . --config Debug/Release

As cmake project dependency

For CMake versions earlier than 3.14, see https://cmake.org/cmake/help/v3.14/module/FetchContent.html

Add to CMakeLists.txt

find_package(cthreads QUIET)
FetchContent_Declare(cthreads
 URL https://github.com/zelang-dev/c-threads/archive/refs/tags/1.0.0.zip
 URL_MD5 0f1c66f911f0912aa2a955a486952a8d
)
FetchContent_MakeAvailable(cthreads)

target_include_directories(${PROJECT_NAME}
  AFTER PUBLIC $<BUILD_INTERFACE:${CTHREADS_INCLUDE_DIR}>
  $<INSTALL_INTERFACE:${CTHREADS_INCLUDE_DIR}>)
target_link_libraries(${PROJECT_NAME} PUBLIC cthreads)