@matheusbsbs / matheus-bagliano / commits / 1570856b51

config.c: avoid xmmap error messages

The config-writing code uses xmmap to map the existing config file, which will die if the map fails. This has two downsides: 1. The error message is not very helpful, as it lacks any context about the file we are mapping: $ mkdir foo $ git config --file=foo some.key value fatal: Out of memory? mmap failed: No such device 2. We normally do not die in this code path; instead, we'd rather report the error and return an appropriate exit status (which is part of the public interface documented in git-config.1). This patch introduces a "gentle" form of xmmap which lets us produce our own error message. We do not want to use mmap directly, because we would like to use the other compatibility elements of xmmap (e.g., handling 0-length maps portably). The end result is: $ git.compile config --file=foo some.key value error: unable to mmap 'foo': No such device $ echo $? 3 Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed May 28, 2015 at 03:56 UTC 1570856b510e3722a3620063e7ba209106b75857

3 files changed +21 -6

config.c

+9 -2

@@ -2048,8 +2048,15 @@ int git_config_set_multivar_in_file(const char *config_filename,

2048

2049 fstat(in_fd, &st);

2050 contents_sz = xsize_t(st.st_size);

2051 - contents = xmmap(NULL, contents_sz, PROT_READ,

2052 - MAP_PRIVATE, in_fd, 0);

2051 + contents = xmmap_gently(NULL, contents_sz, PROT_READ,

2052 + MAP_PRIVATE, in_fd, 0);

2053 + if (contents == MAP_FAILED) {

2054 + error("unable to mmap '%s': %s",

2055 + config_filename, strerror(errno));

2056 + ret = CONFIG_INVALID_FILE;

2057 + contents = NULL;

2058 + goto out_free;

2059 + }

2060 close(in_fd);

2061

2062 if (chmod(lock->filename.buf, st.st_mode & 07777) < 0) {

git-compat-util.h

@@ -623,6 +623,7 @@ extern char *xstrndup(const char *str, size_t len);

623 extern void *xrealloc(void *ptr, size_t size);

624 extern void *xcalloc(size_t nmemb, size_t size);

625 extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);

626 +extern void *xmmap_gently(void *start, size_t length, int prot, int flags, int fd, off_t offset);

627 extern ssize_t xread(int fd, void *buf, size_t len);

628 extern ssize_t xwrite(int fd, const void *buf, size_t len);

629 extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);

sha1_file.c

+11 -4

@@ -707,8 +707,8 @@ static void mmap_limit_check(size_t length)

707 (uintmax_t)length, (uintmax_t)limit);

708 }

709

710 -void *xmmap(void *start, size_t length,

711 - int prot, int flags, int fd, off_t offset)

710 +void *xmmap_gently(void *start, size_t length,

711 + int prot, int flags, int fd, off_t offset)

712 {

713 void *ret;

714

@@ -719,12 +719,19 @@ void *xmmap(void *start, size_t length,

719 return NULL;

720 release_pack_memory(length);

721 ret = mmap(start, length, prot, flags, fd, offset);

722 - if (ret == MAP_FAILED)

723 - die_errno("Out of memory? mmap failed");

722 }

723 return ret;

724 }

725

726 +void *xmmap(void *start, size_t length,

727 + int prot, int flags, int fd, off_t offset)

728 +{

729 + void *ret = xmmap_gently(start, length, prot, flags, fd, offset);

730 + if (ret == MAP_FAILED)

731 + die_errno("Out of memory? mmap failed");

732 + return ret;

733 +}

734 +

735 void close_pack_windows(struct packed_git *p)

736 {

737 while (p->windows) {