musl - musl - an implementation of the standard library for Linux-based systems

musl - an implementation of the standard library for Linux-based systems

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author	Rich Felker <dalias@aerifal.cx>	2013年08月31日 15:50:23 -0400
committer	Rich Felker <dalias@aerifal.cx>	2013年08月31日 15:50:23 -0400
commit	dfddd43256f7ad4bad991eeff5cc51772595f327 (patch)
tree	27e7540262ee86f9cdaaf283efb75230a75e3e89 /src/misc/realpath.c
parent	27b4923ba00f0a7511c7ebf5f19313d6313052e9 (diff)
download	musl-dfddd43256f7ad4bad991eeff5cc51772595f327.tar.gz

debloat realpath's allocation strategy

rather than allocating a PATH_MAX-sized buffer when the caller does not provide an output buffer, work first with a PATH_MAX-sized temp buffer with automatic storage, and either copy it to the caller's buffer or strdup it on success. this not only avoids massive memory waste, but also avoids pulling in free (and thus the full malloc implementation) unnecessarily in static programs.

Diffstat (limited to 'src/misc/realpath.c')

-rw-r--r--

src/misc/realpath.c

1 files changed, 6 insertions, 12 deletions

diff --git a/src/misc/realpath.c b/src/misc/realpath.c
index 2b846497..43d40183 100644
--- a/src/misc/realpath.c
+++ b/src/misc/realpath.c

@@ -5,6 +5,7 @@

#include <fcntl.h>

#include <errno.h>

#include <unistd.h>

+#include <string.h>

void __procfdname(char *, unsigned);

@@ -14,7 +15,7 @@ char *realpath(const char *restrict filename, char *restrict resolved)

ssize_t r;

struct stat st1, st2;

char buf[15+3*sizeof(int)];

- int alloc = 0;

+ char tmp[PATH_MAX];

if (!filename) {

errno = EINVAL;

@@ -25,27 +26,20 @@ char *realpath(const char *restrict filename, char *restrict resolved)

if (fd < 0) return 0;

__procfdname(buf, fd);

- if (!resolved) {

- alloc = 1;

- resolved = malloc(PATH_MAX);

- if (!resolved) return 0;

- }

- r = readlink(buf, resolved, PATH_MAX-1);

+ r = readlink(buf, tmp, sizeof tmp - 1);

if (r < 0) goto err;

- resolved[r] = 0;

+ tmp[r] = 0;

fstat(fd, &st1);

- r = stat(resolved, &st2);

+ r = stat(tmp, &st2);

if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) {

if (!r) errno = ELOOP;

goto err;

}

close(fd);

- return resolved;

+ return resolved ? strcpy(resolved, tmp) : strdup(tmp);

err:

- if (alloc) free(resolved);

close(fd);

return 0;

}

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