Use O_APPEND for stdio append mode.
"Although not explicitly required by this volume of POSIX.1-2008, a good
implementation of append (a) mode would cause the O_APPEND flag to be set."
Yeah, about that...
Bug: N/A
Test: ran tests
Change-Id: I23c4bc5c1ebc92e0cb44025d2d313f321f9ffa68
diff --git a/libc/stdio/stdio.cpp b/libc/stdio/stdio.cpp
index cd4be2e..4d6438b 100644
--- a/libc/stdio/stdio.cpp
+++ b/libc/stdio/stdio.cpp
@@ -68,14 +68,8 @@
_THREAD_PRIVATE_MUTEX(__sfp_mutex);
-// TODO: when we no longer have to support both clang and GCC, we can simplify all this.
-#define SBUF_INIT {0,0}
-#if defined(__LP64__)
-#define MBSTATE_T_INIT {{0},{0}}
-#else
-#define MBSTATE_T_INIT {{0}}
-#endif
-#define WCHAR_IO_DATA_INIT {MBSTATE_T_INIT,MBSTATE_T_INIT,{0},0,0}
+#define SBUF_INIT {}
+#define WCHAR_IO_DATA_INIT {}
static struct __sfileext __sFext[3] = {
{ SBUF_INIT, WCHAR_IO_DATA_INIT, PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP, false, __sseek64 },
@@ -212,11 +206,11 @@
}
FILE* fopen(const char* file, const char* mode) {
- int oflags;
- int flags = __sflags(mode, &oflags);
+ int mode_flags;
+ int flags = __sflags(mode, &mode_flags);
if (flags == 0) return nullptr;
- int fd = open(file, oflags, DEFFILEMODE);
+ int fd = open(file, mode_flags, DEFFILEMODE);
if (fd == -1) {
return nullptr;
}
@@ -228,41 +222,34 @@
return nullptr;
}
- // When opening in append mode, even though we use O_APPEND,
- // we need to seek to the end so that ftell() gets the right
- // answer. If the user then alters the seek pointer, or
- // the file extends, this will fail, but there is not much
- // we can do about this. (We could set __SAPP and check in
- // fseek and ftell.)
- // TODO: check in __sseek instead.
- if (oflags & O_APPEND) __sseek64(fp, 0, SEEK_END);
-
+ // For append mode, even though we use O_APPEND, we need to seek to the end now.
+ if ((mode_flags & O_APPEND) != 0) __sseek64(fp, 0, SEEK_END);
return fp;
}
__strong_alias(fopen64, fopen);
FILE* fdopen(int fd, const char* mode) {
- int oflags;
- int flags = __sflags(mode, &oflags);
+ int mode_flags;
+ int flags = __sflags(mode, &mode_flags);
if (flags == 0) return nullptr;
// Make sure the mode the user wants is a subset of the actual mode.
- int fdflags = fcntl(fd, F_GETFL, 0);
- if (fdflags < 0) return nullptr;
- int tmp = fdflags & O_ACCMODE;
- if (tmp != O_RDWR && (tmp != (oflags & O_ACCMODE))) {
+ int fd_flags = fcntl(fd, F_GETFL, 0);
+ if (fd_flags == -1) return nullptr;
+ int tmp = fd_flags & O_ACCMODE;
+ if (tmp != O_RDWR && (tmp != (mode_flags & O_ACCMODE))) {
errno = EINVAL;
return nullptr;
}
- // If opened for appending, but underlying descriptor does not have
- // O_APPEND bit set, assert __SAPP so that __swrite() will lseek to
- // end before each write.
- // TODO: use fcntl(2) to set O_APPEND instead.
- if ((oflags & O_APPEND) && !(fdflags & O_APPEND)) flags |= __SAPP;
+ // Make sure O_APPEND is set on the underlying fd if our mode has 'a'.
+ // POSIX says we just take the current offset of the underlying fd.
+ if ((mode_flags & O_APPEND) && !(fd_flags & O_APPEND)) {
+ if (fcntl(fd, F_SETFL, fd_flags | O_APPEND) == -1) return nullptr;
+ }
- // If close-on-exec was requested, then turn it on if not already.
- if ((oflags & O_CLOEXEC) && !((tmp = fcntl(fd, F_GETFD)) & FD_CLOEXEC)) {
+ // Make sure O_CLOEXEC is set on the underlying fd if our mode has 'x'.
+ if ((mode_flags & O_CLOEXEC) && !((tmp = fcntl(fd, F_GETFD)) & FD_CLOEXEC)) {
fcntl(fd, F_SETFD, tmp | FD_CLOEXEC);
}
@@ -274,8 +261,8 @@
// all possible, no matter what.
// TODO: rewrite this mess completely.
FILE* freopen(const char* file, const char* mode, FILE* fp) {
- int oflags;
- int flags = __sflags(mode, &oflags);
+ int mode_flags;
+ int flags = __sflags(mode, &mode_flags);
if (flags == 0) {
fclose(fp);
return nullptr;
@@ -307,13 +294,13 @@
}
// Get a new descriptor to refer to the new file.
- int fd = open(file, oflags, DEFFILEMODE);
+ int fd = open(file, mode_flags, DEFFILEMODE);
if (fd < 0 && isopen) {
// If out of fd's close the old one and try again.
if (errno == ENFILE || errno == EMFILE) {
(*fp->_close)(fp->_cookie);
isopen = 0;
- fd = open(file, oflags, DEFFILEMODE);
+ fd = open(file, mode_flags, DEFFILEMODE);
}
}
@@ -346,7 +333,7 @@
// to maintain the descriptor. Various C library routines (perror)
// assume stderr is always fd STDERR_FILENO, even if being freopen'd.
if (wantfd >= 0 && fd != wantfd) {
- if (dup3(fd, wantfd, oflags & O_CLOEXEC) >= 0) {
+ if (dup3(fd, wantfd, mode_flags & O_CLOEXEC) >= 0) {
close(fd);
fd = wantfd;
}
@@ -367,13 +354,8 @@
fp->_close = __sclose;
_EXT(fp)->_seek64 = __sseek64;
- // When opening in append mode, even though we use O_APPEND,
- // we need to seek to the end so that ftell() gets the right
- // answer. If the user then alters the seek pointer, or
- // the file extends, this will fail, but there is not much
- // we can do about this. (We could set __SAPP and check in
- // fseek and ftell.)
- if (oflags & O_APPEND) __sseek64(fp, 0, SEEK_END);
+ // For append mode, even though we use O_APPEND, we need to seek to the end now.
+ if ((mode_flags & O_APPEND) != 0) __sseek64(fp, 0, SEEK_END);
return fp;
}
__strong_alias(freopen64, freopen);
@@ -452,12 +434,6 @@
int __swrite(void* cookie, const char* buf, int n) {
FILE* fp = reinterpret_cast<FILE*>(cookie);
- if (fp->_flags & __SAPP) {
- // The FILE* is in append mode, but the underlying fd doesn't have O_APPEND set.
- // We need to seek manually.
- // TODO: use fcntl(2) to set O_APPEND in fdopen(3) instead?
- TEMP_FAILURE_RETRY(lseek64(fp->_file, 0, SEEK_END));
- }
return TEMP_FAILURE_RETRY(write(fp->_file, buf, n));
}
@@ -496,6 +472,7 @@
static off64_t __ftello64_unlocked(FILE* fp) {
// Find offset of underlying I/O object, then adjust for buffered bytes.
__sflush(fp); // May adjust seek offset on append stream.
+
off64_t result = __seek_unlocked(fp, 0, SEEK_CUR);
if (result == -1) {
return -1;