C Smart Pointers

What this is

This project is an attempt to bring smart pointer constructs to the (GNU) C programming language.

Features

• unique_ptr, shared_ptr macros, and smart type attribute
• Destructor support for cleanup
• Custom variable metadata on allocation
• Cross-platform: tested under linux 3.18.6-1, Mac OS X Yosemite 10.10, and Windows 7 (with MinGW and the Cygwin port of GCC)

Installing

With a package manager

• Mac OS X: brew install snaipe/soft/libcsptr

• AUR: yaourt -S libcsptr

• Ubuntu:

  $ sudo add-apt-repository ppa:snaipewastaken/ppa
  $ sudo apt-get update
  $ sudo apt-get install libcsptr-dev

Building from source

Prerequisites

To compile the library, GCC 4.6+ is needed.

Installation

1. Clone this repository
2. run mkdir build && cd $_ && cmake -DCMAKE_INSTALL_PREFIX=$HOME .. && make && make install
   from the project root for a local install, or run
   mkdir build && cd $_ && cmake -DCMAKE_INSTALL_PREFIX=/usr .. && make && sudo make install for a global install.

Examples

• Simple unique_ptr: simple1.c:

  #include<stdio.h>#include<csptr/smart_ptr.h>intmain(void) {
  // some_int is an unique_ptr to an int with a value of 1.smartint*some_int=unique_ptr(int, 1);
  printf("%p = %d\n", some_int, *some_int);
  // some_int is destroyed herereturn0;
  }

  Shell session:

  $ gcc -std=c99 -o simple1 simple1.c -lcsptr
  $ valgrind ./simple1
  ==3407== Memcheck, a memory error detector
  ==3407== Copyright (C) 2002-2013, and GNU GPL\'d, by Julian Seward et al.
  ==3407== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info
  ==3407== Command: ./test1
  ==3407==
  0x53db068 = 1
  ==3407==
  ==3407== HEAP SUMMARY:
  ==3407== in use at exit: 0 bytes in 0 blocks
  ==3407== total heap usage: 1 allocs, 1 frees, 48 bytes allocated
  ==3407==
  ==3407== All heap blocks were freed -- no leaks are possible
  ==3407==
  ==3407== For counts of detected and suppressed errors, rerun with: -v
  ==3407== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

• Simple unique_ptr with destructor:

  #include<unistd.h>#include<fcntl.h>#include<csptr/smart_ptr.h>structlog_file {
  intfd;
  // ...
  };
  voidcleanup_log_file(void*ptr, void*meta) {
  (void) meta;
  close(((structlog_file*) ptr)->fd);
  }
  intmain(void) {
  smartstructlog_file*log=unique_ptr(structlog_file, {
  .fd=open("/dev/null", O_WRONLY | O_APPEND),
  // ...
  }, cleanup_log_file);
  write(log->fd, "Hello", 5);
  // cleanup_log_file is called, then log is freedreturn0;
  }

• Allocating a smart array and printing its contents before destruction:

  #include<stdio.h>#include<csptr/smart_ptr.h>#include<csptr/array.h>voidprint_int(void*ptr, void*meta) {
  (void) meta;
  // ptr points to the current element// meta points to the array metadata (global to the array), if any.printf("%d\n", *(int*) ptr);
  }
  intmain(void) {
  // Destructors for array types are run on every element of the// array before destruction.smartint*ints=unique_ptr(int[5], {5, 4, 3, 2, 1}, print_int);
  // ints == {5, 4, 3, 2, 1}// Smart arrays are length-awarefor (size_ti=0; i<array_length(ints); ++i) {
  ints[i] =i+1;
  }
  // ints == {1, 2, 3, 4, 5}return0;
  }

More examples

• Using a different memory allocator (although most will replace malloc/free):

  #include<csptr/smart_ptr.h>void*some_allocator(size_t);
  voidsome_deallocator(void*);
  intmain(void) {
  smalloc_allocator= (s_allocator) {some_allocator, some_deallocator};
  // ...return0;
  }

• Automatic cleanup on error cases:

  #include<unistd.h>#include<fcntl.h>#include<csptr/smart_ptr.h>structlog_file {
  intfd;
  // ...
  };
  staticvoidclose_log(void*ptr, void*meta) {
  (void) meta;
  structlog_file*log=ptr;
  if (log->fd!=-1)
  close(log->fd);
  }
  structlog_file*open_log(constchar*path) {
  smartstructlog_file*log=shared_ptr(structlog_file, {0}, close_log);
  if (!log) // failure to allocatereturnNULL; // nothing happens, destructor is not calledlog->fd=open(path, O_WRONLY | O_APPEND | O_CREAT, 0644);
  if (log->fd==-1) // failure to openreturnNULL; // log gets destroyed, file descriptor is not closed since fd == -1.returnsref(log); // a new reference on log is returned, it does not get destoyed
  }
  intmain(void) {
  smartstructlog_file*log=open_log("/dev/null");
  // ...return0; // file descriptor is closed, log is freed
  }

• Using named parameters:

  #include<csptr/smart_ptr.h>voidnothing(void*ptr, void*meta) {}
  intmain(void) {
  struct { inta; } m= { 1 };
  smartint*i=unique_ptr(int,
  .dtor=nothing,
  .value=42,
  .meta= { &m, sizeof (m) }
  );
  return0;
  }

FAQ

Q. Why didn't you use C++ you moron ?
A. Because when I first started this, I was working on a C project. Also, because it's fun.

Q. Can I use this on a serious project ?
A. Yes, but as this project has not been widely used, there might be some bugs. Beware!

Q. How did you make this ?
A. Here's a link to my blog post on the matter.