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Merge branch 'jc/no-writev-does-not-work'

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We used writev() in limited code paths and supplied emulation for
platforms without working writev(), but the emulation was too
faithful to the spec to make the result useless to send even 64kB;
revert the topic and plan to restart the effort later.

* jc/no-writev-does-not-work:
  Revert "compat/posix: introduce writev(3p) wrapper"
  Revert "wrapper: introduce writev(3p) wrappers"
  Revert "sideband: use writev(3p) to send pktlines"
  Revert "cmake: use writev(3p) wrapper as needed"
This commit is contained in:
Junio C Hamano
2026-04-10 16:47:35 -07:00
parent cd412a4962 bfedc73f86
commit 8c9303b1ff
11 changed files with 4 additions and 140 deletions
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4
Makefile
View File

@@ -2029,10 +2029,6 @@ ifdef NO_PREAD
COMPAT_CFLAGS += -DNO_PREAD
COMPAT_OBJS += compat/pread.o
endif
ifdef NO_WRITEV
COMPAT_CFLAGS += -DNO_WRITEV
COMPAT_OBJS += compat/writev.o
endif
ifdef NO_FAST_WORKING_DIRECTORY
BASIC_CFLAGS += -DNO_FAST_WORKING_DIRECTORY
endif

14
compat/posix.h
View File

@@ -137,9 +137,6 @@
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/statvfs.h>
#ifndef NO_WRITEV
#include <sys/uio.h>
#endif
#include <termios.h>
#ifndef NO_SYS_SELECT_H
#include <sys/select.h>
@@ -326,17 +323,6 @@ int git_lstat(const char *, struct stat *);
ssize_t git_pread(int fd, void *buf, size_t count, off_t offset);
#endif
#ifdef NO_WRITEV
#define writev git_writev
#define iovec git_iovec
struct git_iovec {
void *iov_base;
size_t iov_len;
};
ssize_t git_writev(int fd, const struct iovec *iov, int iovcnt);
#endif
#ifdef NO_SETENV
#define setenv gitsetenv
int gitsetenv(const char *, const char *, int);

44
compat/writev.c
View File

@@ -1,44 +0,0 @@
#include "../git-compat-util.h"
#include "../wrapper.h"
ssize_t git_writev(int fd, const struct iovec *iov, int iovcnt)
{
size_t total_written = 0;
size_t sum = 0;
/*
* According to writev(3p), the syscall shall error with EINVAL in case
* the sum of `iov_len` overflows `ssize_t`.
*/
for (int i = 0; i < iovcnt; i++) {
if (iov[i].iov_len > maximum_signed_value_of_type(ssize_t) ||
iov[i].iov_len + sum > maximum_signed_value_of_type(ssize_t)) {
errno = EINVAL;
return -1;
}
sum += iov[i].iov_len;
}
for (int i = 0; i < iovcnt; i++) {
const char *bytes = iov[i].iov_base;
size_t iovec_written = 0;
while (iovec_written < iov[i].iov_len) {
ssize_t bytes_written = xwrite(fd, bytes + iovec_written,
iov[i].iov_len - iovec_written);
if (bytes_written < 0) {
if (total_written)
goto out;
return bytes_written;
}
if (!bytes_written)
goto out;
iovec_written += bytes_written;
total_written += bytes_written;
}
}
out:
return (ssize_t) total_written;
}

2
config.mak.uname
View File

@@ -459,7 +459,6 @@ ifeq ($(uname_S),Windows)
SANE_TOOL_PATH ?= $(msvc_bin_dir_msys)
HAVE_ALLOCA_H = YesPlease
NO_PREAD = YesPlease
NO_WRITEV = YesPlease
NEEDS_CRYPTO_WITH_SSL = YesPlease
NO_LIBGEN_H = YesPlease
NO_POLL = YesPlease
@@ -675,7 +674,6 @@ ifeq ($(uname_S),MINGW)
pathsep = ;
HAVE_ALLOCA_H = YesPlease
NO_PREAD = YesPlease
NO_WRITEV = YesPlease
NEEDS_CRYPTO_WITH_SSL = YesPlease
NO_LIBGEN_H = YesPlease
NO_POLL = YesPlease

6
contrib/buildsystems/CMakeLists.txt
View File

@@ -376,7 +376,7 @@ endif()
#function checks
set(function_checks
strcasestr memmem strlcpy strtoimax strtoumax strtoull
setenv mkdtemp poll pread memmem writev)
setenv mkdtemp poll pread memmem)
#unsetenv,hstrerror are incompatible with windows build
if(NOT WIN32)
@@ -421,10 +421,6 @@ if(NOT HAVE_MEMMEM)
list(APPEND compat_SOURCES compat/memmem.c)
endif()
if(NOT HAVE_WRITEV)
list(APPEND compat_SOURCES compat/writev.c)
endif()
if(NOT WIN32)
if(NOT HAVE_UNSETENV)
list(APPEND compat_SOURCES compat/unsetenv.c)

1
meson.build
View File

@@ -1429,7 +1429,6 @@ checkfuncs = {
'initgroups' : [],
'strtoumax' : ['strtoumax.c', 'strtoimax.c'],
'pread' : ['pread.c'],
'writev' : ['writev.c'],
}
if host_machine.system() == 'windows'

14
sideband.c
View File

@@ -264,7 +264,6 @@ void send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_ma
const char *p = data;
while (sz) {
struct iovec iov[2];
unsigned n;
char hdr[5];
@@ -274,19 +273,12 @@ void send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_ma
if (0 <= band) {
xsnprintf(hdr, sizeof(hdr), "%04x", n + 5);
hdr[4] = band;
iov[0].iov_base = hdr;
iov[0].iov_len = 5;
write_or_die(fd, hdr, 5);
} else {
xsnprintf(hdr, sizeof(hdr), "%04x", n + 4);
iov[0].iov_base = hdr;
iov[0].iov_len = 4;
write_or_die(fd, hdr, 4);
}
iov[1].iov_base = (void *) p;
iov[1].iov_len = n;
writev_or_die(fd, iov, ARRAY_SIZE(iov));
write_or_die(fd, p, n);
p += n;
sz -= n;
}

41
wrapper.c
View File

@@ -323,47 +323,6 @@ ssize_t write_in_full(int fd, const void *buf, size_t count)
return total;
}
ssize_t writev_in_full(int fd, struct iovec *iov, int iovcnt)
{
ssize_t total_written = 0;
while (iovcnt) {
ssize_t bytes_written = writev(fd, iov, iovcnt);
if (bytes_written < 0) {
if (errno == EINTR || errno == EAGAIN)
continue;
return -1;
}
if (!bytes_written) {
errno = ENOSPC;
return -1;
}
total_written += bytes_written;
/*
* We first need to discard any iovec entities that have been
* fully written.
*/
while (iovcnt && (size_t)bytes_written >= iov->iov_len) {
bytes_written -= iov->iov_len;
iov++;
iovcnt--;
}
/*
* Finally, we need to adjust the last iovec in case we have
* performed a partial write.
*/
if (iovcnt && bytes_written) {
iov->iov_base = (char *) iov->iov_base + bytes_written;
iov->iov_len -= bytes_written;
}
}
return total_written;
}
ssize_t pread_in_full(int fd, void *buf, size_t count, off_t offset)
{
char *p = buf;

9
wrapper.h
View File

@@ -47,15 +47,6 @@ ssize_t read_in_full(int fd, void *buf, size_t count);
ssize_t write_in_full(int fd, const void *buf, size_t count);
ssize_t pread_in_full(int fd, void *buf, size_t count, off_t offset);
/*
* Try to write all iovecs. Returns -1 in case an error occurred with a proper
* errno set, the number of bytes written otherwise.
*
* Note that the iovec will be modified as a result of this call to adjust for
* partial writes!
*/
ssize_t writev_in_full(int fd, struct iovec *iov, int iovcnt);
static inline ssize_t write_str_in_full(int fd, const char *str)
{
return write_in_full(fd, str, strlen(str));

8
write-or-die.c
View File

@@ -96,14 +96,6 @@ void write_or_die(int fd, const void *buf, size_t count)
}
}
void writev_or_die(int fd, struct iovec *iov, int iovlen)
{
if (writev_in_full(fd, iov, iovlen) < 0) {
check_pipe(errno);
die_errno("writev error");
}
}
void fwrite_or_die(FILE *f, const void *buf, size_t count)
{
if (fwrite(buf, 1, count, f) != count)

1
write-or-die.h
View File

@@ -7,7 +7,6 @@ void fprintf_or_die(FILE *, const char *fmt, ...);
void fwrite_or_die(FILE *f, const void *buf, size_t count);
void fflush_or_die(FILE *f);
void write_or_die(int fd, const void *buf, size_t count);
void writev_or_die(int fd, struct iovec *iov, int iovlen);
/*
* These values are used to help identify parts of a repository to fsync.