From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/1767 Path: news.gmane.org!not-for-mail From: Gregor Richards Newsgroups: gmane.linux.lib.musl.general Subject: Re: C11 low-hanging fruit Date: Sat, 25 Aug 2012 22:33:39 -0400 Message-ID: <50398B03.9050709@purdue.edu> References: <50397F01.4030503@purdue.edu> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------080206040509090706070005" X-Trace: ger.gmane.org 1345948437 6289 80.91.229.3 (26 Aug 2012 02:33:57 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 26 Aug 2012 02:33:57 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-1768-gllmg-musl=m.gmane.org@lists.openwall.com Sun Aug 26 04:33:58 2012 Return-path: Envelope-to: gllmg-musl@plane.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1T5Sfk-00060U-IX for gllmg-musl@plane.gmane.org; Sun, 26 Aug 2012 04:33:56 +0200 Original-Received: (qmail 21504 invoked by uid 550); 26 Aug 2012 02:33:54 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Original-Received: (qmail 20472 invoked from network); 26 Aug 2012 02:33:53 -0000 User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:14.0) Gecko/20120713 Thunderbird/14.0 In-Reply-To: <50397F01.4030503@purdue.edu> X-PMX-Version: 5.5.9.388399 X-PerlMx-Virus-Scanned: Yes Xref: news.gmane.org gmane.linux.lib.musl.general:1767 Archived-At: This is a multi-part message in MIME format. --------------080206040509090706070005 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit New version of the patch, per chat on IRC: * stdalign.h __GNUC__ test is simplified (since musl isn't going to work well on GCC<3.1 anyway) * feature test macros are simplified, aligned_alloc is unconditional * aligned_alloc is now the fundamental implementation, with posix_memalign in terms of it instead of the opposite * the check for 'x' in fopen is simplified, as well as the check for '+' With valediction, - Gregor Richards On 08/25/2012 09:42 PM, Gregor Richards wrote: > Attached is a diff that adds the trivially-simple bits of C11. That > is, those that require changes to the standard headers, but very > little in the way of implementation. Included are: > * stdalign.h , including backwards compatibility for GCC. > * aligned_alloc > * fopen(..., "...x") > * conditional removal of gets > > Excluded are: > * threads.h (waiting to see glibc's ABI) > * stdatomic.h (complicated, probably has ABI implications too, not > even fully supported by GCC yet) > * uchar.h (this is MOSTLY trivial since musl's wchar is Unicode > anyway, but char32_t makes it a bit more than some weak aliases) > * at_quick_exit, quick_exit (I suspect that our benevolent dictator > will have a lot to say in exactly what makes an exit "quick" or not, > so I'm not touching this) > > I used __STDC_VERSION__ in the headers to control exposure of > aligned_alloc and gets. aligned_alloc I additionally exposed with the > non-standard feature test macro _ISOC11_SOURCE, for the simple reason > that glibc does it; if you have a non-C11 compiler but C11 libc, > -D_ISOC11_SOURCE is a much less gross way to get aligned_alloc than > -D_GNU_SOURCE, anyway :) > > With valediction, > - Gregor Richards > --------------080206040509090706070005 Content-Type: text/x-diff; name="c11-easy.diff" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="c11-easy.diff" diff --git a/include/stdalign.h b/include/stdalign.h new file mode 100644 --- /dev/null +++ b/include/stdalign.h @@ -0,0 +1,23 @@ +#ifndef _STDALIGN_H +#define _STDALIGN_H + +/* this whole header only works in C11 or with compiler extensions */ +#if __STDC_VERSION__ < 201112L + +#if __GNUC__ +#define _Alignas(t) __attribute__((__aligned__(t))) +#define _Alignof(t) __alignof__(t) + +#else +#error stdalign.h is only supported with C11 or GNU extensions + +#endif + +#endif + +#define alignas _Alignas +#define alignof _Alignof +#define __alignas_is_defined 1 +#define __alignof_is_defined 1 + +#endif diff --git a/include/stdio.h b/include/stdio.h --- a/include/stdio.h +++ b/include/stdio.h @@ -90,7 +90,9 @@ int putchar(int); char *fgets(char *, int, FILE *); +#if __STDC_VERSION__ < 201112L char *gets(char *); +#endif int fputs(const char *, FILE *); int puts(const char *); diff --git a/include/stdlib.h b/include/stdlib.h --- a/include/stdlib.h +++ b/include/stdlib.h @@ -102,6 +102,8 @@ #endif +void *aligned_alloc(size_t alignment, size_t size); + #if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \ || defined(_BSD_SOURCE) diff --git a/src/malloc/aligned_alloc.c b/src/malloc/aligned_alloc.c new file mode 100644 --- /dev/null +++ b/src/malloc/aligned_alloc.c @@ -0,0 +1,51 @@ +#include +#include +#include + +/* This function should work with most dlmalloc-like chunk bookkeeping + * systems, but it's only guaranteed to work with the native implementation + * used in this library. */ + +void *aligned_alloc(size_t align, size_t len) +{ + unsigned char *mem, *new, *end; + size_t header, footer; + + if ((align & -align & -sizeof(void *)) != align) { + errno = EINVAL; + return NULL; + } + + if (len > SIZE_MAX - align) { + errno = ENOMEM; + return NULL; + } + + if (align <= 4*sizeof(size_t)) { + if (!(mem = malloc(len))) + return NULL; + return mem; + } + + if (!(mem = malloc(len + align-1))) + return NULL; + + header = ((size_t *)mem)[-1]; + end = mem + (header & -8); + footer = ((size_t *)end)[-2]; + new = (void *)((uintptr_t)mem + align-1 & -align); + + if (!(header & 7)) { + ((size_t *)new)[-2] = ((size_t *)mem)[-2] + (new-mem); + ((size_t *)new)[-1] = ((size_t *)mem)[-1] - (new-mem); + return new; + } + + ((size_t *)mem)[-1] = header&7 | new-mem; + ((size_t *)new)[-2] = footer&7 | new-mem; + ((size_t *)new)[-1] = header&7 | end-new; + ((size_t *)end)[-2] = footer&7 | end-new; + + if (new != mem) free(mem); + return new; +} diff --git a/src/malloc/posix_memalign.c b/src/malloc/posix_memalign.c --- a/src/malloc/posix_memalign.c +++ b/src/malloc/posix_memalign.c @@ -1,47 +1,12 @@ #include -#include -#include - -/* This function should work with most dlmalloc-like chunk bookkeeping - * systems, but it's only guaranteed to work with the native implementation - * used in this library. */ int posix_memalign(void **res, size_t align, size_t len) { - unsigned char *mem, *new, *end; - size_t header, footer; - - if ((align & -align & -sizeof(void *)) != align) return EINVAL; - if (len > SIZE_MAX - align) return ENOMEM; - - if (align <= 4*sizeof(size_t)) { - if (!(mem = malloc(len))) - return errno; + void *mem = allocate_aligned(align, len); + if (mem) { *res = mem; return 0; + } else { + return errno; } - - if (!(mem = malloc(len + align-1))) - return errno; - - header = ((size_t *)mem)[-1]; - end = mem + (header & -8); - footer = ((size_t *)end)[-2]; - new = (void *)((uintptr_t)mem + align-1 & -align); - - if (!(header & 7)) { - ((size_t *)new)[-2] = ((size_t *)mem)[-2] + (new-mem); - ((size_t *)new)[-1] = ((size_t *)mem)[-1] - (new-mem); - *res = new; - return 0; - } - - ((size_t *)mem)[-1] = header&7 | new-mem; - ((size_t *)new)[-2] = footer&7 | new-mem; - ((size_t *)new)[-1] = header&7 | end-new; - ((size_t *)end)[-2] = footer&7 | end-new; - - if (new != mem) free(mem); - *res = new; - return 0; } diff --git a/src/stdio/fopen.c b/src/stdio/fopen.c --- a/src/stdio/fopen.c +++ b/src/stdio/fopen.c @@ -5,7 +5,6 @@ FILE *f; int fd; int flags; - int plus = !!strchr(mode, '+'); /* Check for valid initial mode character */ if (!strchr("rwa", *mode)) { @@ -14,9 +13,10 @@ } /* Compute the flags to pass to open() */ - if (plus) flags = O_RDWR; + if (strchr(mode, '+')) flags = O_RDWR; else if (*mode == 'r') flags = O_RDONLY; else flags = O_WRONLY; + if (strchr(mode, 'x')) flags |= O_EXCL; if (*mode != 'r') flags |= O_CREAT; if (*mode == 'w') flags |= O_TRUNC; if (*mode == 'a') flags |= O_APPEND; --------------080206040509090706070005--