Hi, I propose this patch to make realpath(3) conform to SUSv4. It is somewhat inspired by FreeBSD. When the second argument "resolved" of realpath(3) is set to NULL, the behaviour is "implementation-defined" according to IEEE Std 1003.1-2004[1], however IEEE Std 1003.1-2008 specifies that realpath(3) should allocate memory in that case[2]. Currently, in OpenBSD, a program segfaults if it calls realpath with resolved set to NULL. I also tweaked some errno values to comply with SUSv4. The standard also says that the C99 "restrict" keyword should be used in the prototype of the function but I don't know if this breaks some old platforms.
1: http://pubs.opengroup.org/onlinepubs/009695399/functions/realpath.html 2: http://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html (Please bear with me as this is my first time in libc and mdoc) Best regards, Jona Index: realpath.3 =================================================================== RCS file: /cvs/src/lib/libc/stdlib/realpath.3,v retrieving revision 1.15 diff -u -p -r1.15 realpath.3 --- realpath.3 6 Jul 2007 15:42:04 -0000 1.15 +++ realpath.3 10 Jul 2011 13:55:40 -0000 @@ -30,7 +30,7 @@ .\" .\" $OpenBSD: realpath.3,v 1.15 2007/07/06 15:42:04 millert Exp $ .\" -.Dd $Mdocdate: July 6 2007 $ +.Dd $Mdocdate: July 10 2011 $ .Dt REALPATH 3 .Os .Sh NAME @@ -40,7 +40,7 @@ .Fd #include <limits.h> .Fd #include <stdlib.h> .Ft "char *" -.Fn realpath "const char *pathname" "char resolved[PATH_MAX]" +.Fn realpath "const char *pathname" "char *resolved" .Sh DESCRIPTION The .Fn realpath @@ -60,7 +60,8 @@ argument .Em must refer to a buffer capable of storing at least .Dv PATH_MAX -characters. +characters, or be +.Dv NULL . .Pp The .Fn realpath @@ -78,6 +79,13 @@ The function returns .Fa resolved on success. +If +.Dv NULL +was provided as +.Fa resolved +and no error was caused, then +.Fa realpath +returns a null-terminated string in a newly allocated buffer. If an error occurs, .Fn realpath returns @@ -98,6 +106,11 @@ and .Sh SEE ALSO .Xr readlink 1 , .Xr getcwd 3 +.Sh STANDARDS +The +.Fn realpath +function conforms to +.St -p1003.1-2008 . .Sh HISTORY The .Fn realpath Index: realpath.c =================================================================== RCS file: /cvs/src/lib/libc/stdlib/realpath.c,v retrieving revision 1.13 diff -u -p -r1.13 realpath.c --- realpath.c 8 Aug 2005 08:05:37 -0000 1.13 +++ realpath.c 10 Jul 2011 13:55:40 -0000 @@ -43,16 +43,34 @@ * in which case the path which caused trouble is left in (resolved). */ char * -realpath(const char *path, char resolved[PATH_MAX]) +realpath(const char *path, char *resolved) { struct stat sb; char *p, *q, *s; size_t left_len, resolved_len; unsigned symlinks; - int serrno, slen; + int serrno, slen, mem_allocated; char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; + if (path == NULL) { + errno = EINVAL; + return (NULL); + } + if (path[0] == '\0') { + errno = ENOENT; + return (NULL); + } + serrno = errno; + + if (resolved == NULL) { + resolved = malloc(PATH_MAX); + if (resolved == NULL) + return (NULL); + mem_allocated = 1; + } else + mem_allocated = 0; + symlinks = 0; if (path[0] == '/') { resolved[0] = '/'; @@ -63,7 +81,10 @@ realpath(const char *path, char resolved left_len = strlcpy(left, path + 1, sizeof(left)); } else { if (getcwd(resolved, PATH_MAX) == NULL) { - strlcpy(resolved, ".", PATH_MAX); + if (mem_allocated) + free(resolved); + else + strlcpy(resolved, ".", PATH_MAX); return (NULL); } resolved_len = strlen(resolved); @@ -71,7 +92,7 @@ realpath(const char *path, char resolved } if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { errno = ENAMETOOLONG; - return (NULL); + goto err; } /* @@ -86,7 +107,7 @@ realpath(const char *path, char resolved s = p ? p : left + left_len; if (s - left >= sizeof(next_token)) { errno = ENAMETOOLONG; - return (NULL); + goto err; } memcpy(next_token, left, s - left); next_token[s - left] = '\0'; @@ -96,7 +117,7 @@ realpath(const char *path, char resolved if (resolved[resolved_len - 1] != '/') { if (resolved_len + 1 >= PATH_MAX) { errno = ENAMETOOLONG; - return (NULL); + goto err; } resolved[resolved_len++] = '/'; resolved[resolved_len] = '\0'; @@ -127,23 +148,23 @@ realpath(const char *path, char resolved resolved_len = strlcat(resolved, next_token, PATH_MAX); if (resolved_len >= PATH_MAX) { errno = ENAMETOOLONG; - return (NULL); + goto err; } if (lstat(resolved, &sb) != 0) { if (errno == ENOENT && p == NULL) { errno = serrno; return (resolved); } - return (NULL); + goto err; } if (S_ISLNK(sb.st_mode)) { if (symlinks++ > MAXSYMLINKS) { errno = ELOOP; - return (NULL); + goto err; } slen = readlink(resolved, symlink, sizeof(symlink) - 1); if (slen < 0) - return (NULL); + goto err; symlink[slen] = '\0'; if (symlink[0] == '/') { resolved[1] = 0; @@ -165,7 +186,7 @@ realpath(const char *path, char resolved if (symlink[slen - 1] != '/') { if (slen + 1 >= sizeof(symlink)) { errno = ENAMETOOLONG; - return (NULL); + goto err; } symlink[slen] = '/'; symlink[slen + 1] = 0; @@ -173,7 +194,7 @@ realpath(const char *path, char resolved left_len = strlcat(symlink, left, sizeof(left)); if (left_len >= sizeof(left)) { errno = ENAMETOOLONG; - return (NULL); + goto err; } } left_len = strlcpy(left, symlink, sizeof(left)); @@ -187,4 +208,9 @@ realpath(const char *path, char resolved if (resolved_len > 1 && resolved[resolved_len - 1] == '/') resolved[resolved_len - 1] = '\0'; return (resolved); + +err: + if (mem_allocated) + free(resolved); + return (NULL); }
