git/wrapper.c
Ævar Arnfjörð Bjarmason 3540c71ea5 wrapper.c: add x{un,}setenv(), and use xsetenv() in environment.c
Add fatal wrappers for setenv() and unsetenv(). In d7ac12b25d (Add
set_git_dir() function, 2007-08-01) we started checking its return
value, and since 48988c4d0c (set_git_dir: die when setenv() fails,
2018-03-30) we've had set_git_dir_1() die if we couldn't set it.

Let's provide a wrapper for both, this will be useful in many other
places, a subsequent patch will make another use of xsetenv().

The checking of the return value here is over-eager according to
setenv(3) and POSIX. It's documented as returning just -1 or 0, so
perhaps we should be checking -1 explicitly.

Let's just instead die on any non-zero, if our C library is so broken
as to return something else than -1 on error (and perhaps not set
errno?) the worst we'll do is die with a nonsensical errno value, but
we'll want to die in either case.

Let's make these return "void" instead of "int". As far as I can tell
there's no other x*() wrappers that needed to make the decision of
deviating from the signature in the C library, but since their return
value is only used to indicate errors (so we'd die here), we can catch
unreachable code such as

    if (xsetenv(...) < 0)
        [...];

I think it would be OK skip the NULL check of the "name" here for the
calls to die_errno(). Almost all of our setenv() callers are taking a
constant string hardcoded in the source as the first argument, and for
the rest we can probably assume they've done the NULL check
themselves. Even if they didn't, modern C libraries are forgiving
about it (e.g. glibc formatting it as "(null)"), on those that aren't,
well, we were about to die anyway. But let's include the check anyway
for good measure.

1. https://pubs.opengroup.org/onlinepubs/009604499/functions/setenv.html

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-09-22 13:15:00 -07:00

711 lines
15 KiB
C

/*
* Various trivial helper wrappers around standard functions
*/
#include "cache.h"
#include "config.h"
static int memory_limit_check(size_t size, int gentle)
{
static size_t limit = 0;
if (!limit) {
limit = git_env_ulong("GIT_ALLOC_LIMIT", 0);
if (!limit)
limit = SIZE_MAX;
}
if (size > limit) {
if (gentle) {
error("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
(uintmax_t)size, (uintmax_t)limit);
return -1;
} else
die("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
(uintmax_t)size, (uintmax_t)limit);
}
return 0;
}
char *xstrdup(const char *str)
{
char *ret = strdup(str);
if (!ret)
die("Out of memory, strdup failed");
return ret;
}
static void *do_xmalloc(size_t size, int gentle)
{
void *ret;
if (memory_limit_check(size, gentle))
return NULL;
ret = malloc(size);
if (!ret && !size)
ret = malloc(1);
if (!ret) {
if (!gentle)
die("Out of memory, malloc failed (tried to allocate %lu bytes)",
(unsigned long)size);
else {
error("Out of memory, malloc failed (tried to allocate %lu bytes)",
(unsigned long)size);
return NULL;
}
}
#ifdef XMALLOC_POISON
memset(ret, 0xA5, size);
#endif
return ret;
}
void *xmalloc(size_t size)
{
return do_xmalloc(size, 0);
}
static void *do_xmallocz(size_t size, int gentle)
{
void *ret;
if (unsigned_add_overflows(size, 1)) {
if (gentle) {
error("Data too large to fit into virtual memory space.");
return NULL;
} else
die("Data too large to fit into virtual memory space.");
}
ret = do_xmalloc(size + 1, gentle);
if (ret)
((char*)ret)[size] = 0;
return ret;
}
void *xmallocz(size_t size)
{
return do_xmallocz(size, 0);
}
void *xmallocz_gently(size_t size)
{
return do_xmallocz(size, 1);
}
/*
* xmemdupz() allocates (len + 1) bytes of memory, duplicates "len" bytes of
* "data" to the allocated memory, zero terminates the allocated memory,
* and returns a pointer to the allocated memory. If the allocation fails,
* the program dies.
*/
void *xmemdupz(const void *data, size_t len)
{
return memcpy(xmallocz(len), data, len);
}
char *xstrndup(const char *str, size_t len)
{
char *p = memchr(str, '\0', len);
return xmemdupz(str, p ? p - str : len);
}
int xstrncmpz(const char *s, const char *t, size_t len)
{
int res = strncmp(s, t, len);
if (res)
return res;
return s[len] == '\0' ? 0 : 1;
}
void *xrealloc(void *ptr, size_t size)
{
void *ret;
if (!size) {
free(ptr);
return xmalloc(0);
}
memory_limit_check(size, 0);
ret = realloc(ptr, size);
if (!ret)
die("Out of memory, realloc failed");
return ret;
}
void *xcalloc(size_t nmemb, size_t size)
{
void *ret;
if (unsigned_mult_overflows(nmemb, size))
die("data too large to fit into virtual memory space");
memory_limit_check(size * nmemb, 0);
ret = calloc(nmemb, size);
if (!ret && (!nmemb || !size))
ret = calloc(1, 1);
if (!ret)
die("Out of memory, calloc failed");
return ret;
}
void xsetenv(const char *name, const char *value, int overwrite)
{
if (setenv(name, value, overwrite))
die_errno(_("could not setenv '%s'"), name ? name : "(null)");
}
void xunsetenv(const char *name)
{
if (!unsetenv(name))
die_errno(_("could not unsetenv '%s'"), name ? name : "(null)");
}
/*
* Limit size of IO chunks, because huge chunks only cause pain. OS X
* 64-bit is buggy, returning EINVAL if len >= INT_MAX; and even in
* the absence of bugs, large chunks can result in bad latencies when
* you decide to kill the process.
*
* We pick 8 MiB as our default, but if the platform defines SSIZE_MAX
* that is smaller than that, clip it to SSIZE_MAX, as a call to
* read(2) or write(2) larger than that is allowed to fail. As the last
* resort, we allow a port to pass via CFLAGS e.g. "-DMAX_IO_SIZE=value"
* to override this, if the definition of SSIZE_MAX given by the platform
* is broken.
*/
#ifndef MAX_IO_SIZE
# define MAX_IO_SIZE_DEFAULT (8*1024*1024)
# if defined(SSIZE_MAX) && (SSIZE_MAX < MAX_IO_SIZE_DEFAULT)
# define MAX_IO_SIZE SSIZE_MAX
# else
# define MAX_IO_SIZE MAX_IO_SIZE_DEFAULT
# endif
#endif
/**
* xopen() is the same as open(), but it die()s if the open() fails.
*/
int xopen(const char *path, int oflag, ...)
{
mode_t mode = 0;
va_list ap;
/*
* va_arg() will have undefined behavior if the specified type is not
* compatible with the argument type. Since integers are promoted to
* ints, we fetch the next argument as an int, and then cast it to a
* mode_t to avoid undefined behavior.
*/
va_start(ap, oflag);
if (oflag & O_CREAT)
mode = va_arg(ap, int);
va_end(ap);
for (;;) {
int fd = open(path, oflag, mode);
if (fd >= 0)
return fd;
if (errno == EINTR)
continue;
if ((oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
die_errno(_("unable to create '%s'"), path);
else if ((oflag & O_RDWR) == O_RDWR)
die_errno(_("could not open '%s' for reading and writing"), path);
else if ((oflag & O_WRONLY) == O_WRONLY)
die_errno(_("could not open '%s' for writing"), path);
else
die_errno(_("could not open '%s' for reading"), path);
}
}
static int handle_nonblock(int fd, short poll_events, int err)
{
struct pollfd pfd;
if (err != EAGAIN && err != EWOULDBLOCK)
return 0;
pfd.fd = fd;
pfd.events = poll_events;
/*
* no need to check for errors, here;
* a subsequent read/write will detect unrecoverable errors
*/
poll(&pfd, 1, -1);
return 1;
}
/*
* xread() is the same a read(), but it automatically restarts read()
* operations with a recoverable error (EAGAIN and EINTR). xread()
* DOES NOT GUARANTEE that "len" bytes is read even if the data is available.
*/
ssize_t xread(int fd, void *buf, size_t len)
{
ssize_t nr;
if (len > MAX_IO_SIZE)
len = MAX_IO_SIZE;
while (1) {
nr = read(fd, buf, len);
if (nr < 0) {
if (errno == EINTR)
continue;
if (handle_nonblock(fd, POLLIN, errno))
continue;
}
return nr;
}
}
/*
* xwrite() is the same a write(), but it automatically restarts write()
* operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT
* GUARANTEE that "len" bytes is written even if the operation is successful.
*/
ssize_t xwrite(int fd, const void *buf, size_t len)
{
ssize_t nr;
if (len > MAX_IO_SIZE)
len = MAX_IO_SIZE;
while (1) {
nr = write(fd, buf, len);
if (nr < 0) {
if (errno == EINTR)
continue;
if (handle_nonblock(fd, POLLOUT, errno))
continue;
}
return nr;
}
}
/*
* xpread() is the same as pread(), but it automatically restarts pread()
* operations with a recoverable error (EAGAIN and EINTR). xpread() DOES
* NOT GUARANTEE that "len" bytes is read even if the data is available.
*/
ssize_t xpread(int fd, void *buf, size_t len, off_t offset)
{
ssize_t nr;
if (len > MAX_IO_SIZE)
len = MAX_IO_SIZE;
while (1) {
nr = pread(fd, buf, len, offset);
if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
continue;
return nr;
}
}
ssize_t read_in_full(int fd, void *buf, size_t count)
{
char *p = buf;
ssize_t total = 0;
while (count > 0) {
ssize_t loaded = xread(fd, p, count);
if (loaded < 0)
return -1;
if (loaded == 0)
return total;
count -= loaded;
p += loaded;
total += loaded;
}
return total;
}
ssize_t write_in_full(int fd, const void *buf, size_t count)
{
const char *p = buf;
ssize_t total = 0;
while (count > 0) {
ssize_t written = xwrite(fd, p, count);
if (written < 0)
return -1;
if (!written) {
errno = ENOSPC;
return -1;
}
count -= written;
p += written;
total += written;
}
return total;
}
ssize_t pread_in_full(int fd, void *buf, size_t count, off_t offset)
{
char *p = buf;
ssize_t total = 0;
while (count > 0) {
ssize_t loaded = xpread(fd, p, count, offset);
if (loaded < 0)
return -1;
if (loaded == 0)
return total;
count -= loaded;
p += loaded;
total += loaded;
offset += loaded;
}
return total;
}
int xdup(int fd)
{
int ret = dup(fd);
if (ret < 0)
die_errno("dup failed");
return ret;
}
/**
* xfopen() is the same as fopen(), but it die()s if the fopen() fails.
*/
FILE *xfopen(const char *path, const char *mode)
{
for (;;) {
FILE *fp = fopen(path, mode);
if (fp)
return fp;
if (errno == EINTR)
continue;
if (*mode && mode[1] == '+')
die_errno(_("could not open '%s' for reading and writing"), path);
else if (*mode == 'w' || *mode == 'a')
die_errno(_("could not open '%s' for writing"), path);
else
die_errno(_("could not open '%s' for reading"), path);
}
}
FILE *xfdopen(int fd, const char *mode)
{
FILE *stream = fdopen(fd, mode);
if (stream == NULL)
die_errno("Out of memory? fdopen failed");
return stream;
}
FILE *fopen_for_writing(const char *path)
{
FILE *ret = fopen(path, "w");
if (!ret && errno == EPERM) {
if (!unlink(path))
ret = fopen(path, "w");
else
errno = EPERM;
}
return ret;
}
static void warn_on_inaccessible(const char *path)
{
warning_errno(_("unable to access '%s'"), path);
}
int warn_on_fopen_errors(const char *path)
{
if (errno != ENOENT && errno != ENOTDIR) {
warn_on_inaccessible(path);
return -1;
}
return 0;
}
FILE *fopen_or_warn(const char *path, const char *mode)
{
FILE *fp = fopen(path, mode);
if (fp)
return fp;
warn_on_fopen_errors(path);
return NULL;
}
int xmkstemp(char *filename_template)
{
int fd;
char origtemplate[PATH_MAX];
strlcpy(origtemplate, filename_template, sizeof(origtemplate));
fd = mkstemp(filename_template);
if (fd < 0) {
int saved_errno = errno;
const char *nonrelative_template;
if (strlen(filename_template) != strlen(origtemplate))
filename_template = origtemplate;
nonrelative_template = absolute_path(filename_template);
errno = saved_errno;
die_errno("Unable to create temporary file '%s'",
nonrelative_template);
}
return fd;
}
/* Adapted from libiberty's mkstemp.c. */
#undef TMP_MAX
#define TMP_MAX 16384
int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
{
static const char letters[] =
"abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"0123456789";
static const int num_letters = ARRAY_SIZE(letters) - 1;
static const char x_pattern[] = "XXXXXX";
static const int num_x = ARRAY_SIZE(x_pattern) - 1;
uint64_t value;
struct timeval tv;
char *filename_template;
size_t len;
int fd, count;
len = strlen(pattern);
if (len < num_x + suffix_len) {
errno = EINVAL;
return -1;
}
if (strncmp(&pattern[len - num_x - suffix_len], x_pattern, num_x)) {
errno = EINVAL;
return -1;
}
/*
* Replace pattern's XXXXXX characters with randomness.
* Try TMP_MAX different filenames.
*/
gettimeofday(&tv, NULL);
value = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec ^ getpid();
filename_template = &pattern[len - num_x - suffix_len];
for (count = 0; count < TMP_MAX; ++count) {
uint64_t v = value;
int i;
/* Fill in the random bits. */
for (i = 0; i < num_x; i++) {
filename_template[i] = letters[v % num_letters];
v /= num_letters;
}
fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
if (fd >= 0)
return fd;
/*
* Fatal error (EPERM, ENOSPC etc).
* It doesn't make sense to loop.
*/
if (errno != EEXIST)
break;
/*
* This is a random value. It is only necessary that
* the next TMP_MAX values generated by adding 7777 to
* VALUE are different with (module 2^32).
*/
value += 7777;
}
/* We return the null string if we can't find a unique file name. */
pattern[0] = '\0';
return -1;
}
int git_mkstemp_mode(char *pattern, int mode)
{
/* mkstemp is just mkstemps with no suffix */
return git_mkstemps_mode(pattern, 0, mode);
}
int xmkstemp_mode(char *filename_template, int mode)
{
int fd;
char origtemplate[PATH_MAX];
strlcpy(origtemplate, filename_template, sizeof(origtemplate));
fd = git_mkstemp_mode(filename_template, mode);
if (fd < 0) {
int saved_errno = errno;
const char *nonrelative_template;
if (!filename_template[0])
filename_template = origtemplate;
nonrelative_template = absolute_path(filename_template);
errno = saved_errno;
die_errno("Unable to create temporary file '%s'",
nonrelative_template);
}
return fd;
}
static int warn_if_unremovable(const char *op, const char *file, int rc)
{
int err;
if (!rc || errno == ENOENT)
return 0;
err = errno;
warning_errno("unable to %s '%s'", op, file);
errno = err;
return rc;
}
int unlink_or_msg(const char *file, struct strbuf *err)
{
int rc = unlink(file);
assert(err);
if (!rc || errno == ENOENT)
return 0;
strbuf_addf(err, "unable to unlink '%s': %s",
file, strerror(errno));
return -1;
}
int unlink_or_warn(const char *file)
{
return warn_if_unremovable("unlink", file, unlink(file));
}
int rmdir_or_warn(const char *file)
{
return warn_if_unremovable("rmdir", file, rmdir(file));
}
int remove_or_warn(unsigned int mode, const char *file)
{
return S_ISGITLINK(mode) ? rmdir_or_warn(file) : unlink_or_warn(file);
}
static int access_error_is_ok(int err, unsigned flag)
{
return (is_missing_file_error(err) ||
((flag & ACCESS_EACCES_OK) && err == EACCES));
}
int access_or_warn(const char *path, int mode, unsigned flag)
{
int ret = access(path, mode);
if (ret && !access_error_is_ok(errno, flag))
warn_on_inaccessible(path);
return ret;
}
int access_or_die(const char *path, int mode, unsigned flag)
{
int ret = access(path, mode);
if (ret && !access_error_is_ok(errno, flag))
die_errno(_("unable to access '%s'"), path);
return ret;
}
char *xgetcwd(void)
{
struct strbuf sb = STRBUF_INIT;
if (strbuf_getcwd(&sb))
die_errno(_("unable to get current working directory"));
return strbuf_detach(&sb, NULL);
}
int xsnprintf(char *dst, size_t max, const char *fmt, ...)
{
va_list ap;
int len;
va_start(ap, fmt);
len = vsnprintf(dst, max, fmt, ap);
va_end(ap);
if (len < 0)
BUG("your snprintf is broken");
if (len >= max)
BUG("attempt to snprintf into too-small buffer");
return len;
}
void write_file_buf(const char *path, const char *buf, size_t len)
{
int fd = xopen(path, O_WRONLY | O_CREAT | O_TRUNC, 0666);
if (write_in_full(fd, buf, len) < 0)
die_errno(_("could not write to '%s'"), path);
if (close(fd))
die_errno(_("could not close '%s'"), path);
}
void write_file(const char *path, const char *fmt, ...)
{
va_list params;
struct strbuf sb = STRBUF_INIT;
va_start(params, fmt);
strbuf_vaddf(&sb, fmt, params);
va_end(params);
strbuf_complete_line(&sb);
write_file_buf(path, sb.buf, sb.len);
strbuf_release(&sb);
}
void sleep_millisec(int millisec)
{
poll(NULL, 0, millisec);
}
int xgethostname(char *buf, size_t len)
{
/*
* If the full hostname doesn't fit in buf, POSIX does not
* specify whether the buffer will be null-terminated, so to
* be safe, do it ourselves.
*/
int ret = gethostname(buf, len);
if (!ret)
buf[len - 1] = 0;
return ret;
}
int is_empty_or_missing_file(const char *filename)
{
struct stat st;
if (stat(filename, &st) < 0) {
if (errno == ENOENT)
return 1;
die_errno(_("could not stat %s"), filename);
}
return !st.st_size;
}
int open_nofollow(const char *path, int flags)
{
#ifdef O_NOFOLLOW
return open(path, flags | O_NOFOLLOW);
#else
struct stat st;
if (lstat(path, &st) < 0)
return -1;
if (S_ISLNK(st.st_mode)) {
errno = ELOOP;
return -1;
}
return open(path, flags);
#endif
}