Add realpath(3).

libc/Makefile

@@ -213,6 +213,7 @@ raise.o \
 rand.o \
 readdirents.o \
 read.o \
+realpath.o \
 removeat.o \
 remove.o \
 renameat.o \

libc/include/stdlib.h

@@ -89,6 +89,7 @@ int putenv(char*);
 void qsort(void*, size_t, size_t, int (*)(const void*, const void*));
 int rand(void);
 void* realloc(void*, size_t);
+char* realpath(const char* restrict, char* restrict);
 int setenv(const char*, const char*, int);
 void srand(unsigned);
 long strtol(const char* restrict, char** restrict, int);
@@ -139,7 +140,6 @@ int posix_memalign(void**, size_t, size_t);
 int posix_openpt(int);
 char* ptsname(int);
 long random(void);
-char* realpath(const char* restrict, char* restrict);
 unsigned short *seed48(unsigned short [3]);
 void setkey(const char*);
 char* setstate(char*);

libc/realpath.cpp

@@ -0,0 +1,57 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of the Sortix C Library.
+
+    The Sortix C Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    The Sortix C Library is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
+
+    realpath.cpp
+    Return the canonicalized filename.
+
+*******************************************************************************/
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+char* realpath(const char* restrict path, char* restrict resolved_path)
+{
+	char* ret_path = canonicalize_file_name(path);
+	if ( !ret_path )
+		return NULL;
+	if ( !resolved_path )
+		return ret_path;
+#ifdef PATH_MAX
+	if ( PATH_MAX < strlen(ret_path) + 1 )
+		return errno = ENAMETOOLONG, (char*) NULL;
+	strcpy(resolved_path, ret_path);
+	free(ret_path);
+	return resolved_path;
+#else
+	if ( !isatty(2) )
+		dup2(open("/dev/tty", O_WRONLY), 2);
+	fprintf(stderr, "%s:%u: %s(\"%s\", %p) = \"%s\": "
+	        "This platform doesn't have PATH_MAX and the second argument "
+	        "wasn't NULL - You cannot reliably allocate a sufficiently large "
+	        "buffer and the POSIX standard specifies this as undefined "
+	        "behavior, aborting.\n", __FILE__, __LINE__, __func__, path,
+	        resolved_path, ret_path);
+	abort();
+#endif
+}