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Re: [PATCH] fflush: avoid warnings on modern systems
From: |
Jim Meyering |
Subject: |
Re: [PATCH] fflush: avoid warnings on modern systems |
Date: |
Mon, 26 Jan 2009 22:33:03 +0100 |
Eric Blake <address@hidden> wrote:
> According to Jim Meyering on 1/26/2009 10:34 AM:
>> Annoyed that portability cruft is evoking warnings,
>> I propose to add even more cruft ;-)
>> What do you think?
>>
>> Is it worth reindenting for the outer (pos-enclosing) braces I added?
>> I presume C99 decl-after-code is not an option.
>
> The idea looks fine, and you are correct that gnulib should stick with
> C89. Go ahead and reindent, then commit.
I've also moved the declaration of "pos" down
to the first use, and avoided introducing a bug (I nearly
left a use of "result" outside of its new, more-limited scope).
>From 02a5e81cd5159cf787b725fdf4bf8e712b67ccff Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Mon, 26 Jan 2009 18:32:23 +0100
Subject: [PATCH] fflush: avoid warnings on modern systems
* lib/fflush.c (rpl_fflush): Move declarations of locals,
pos and result, into scopes where they're used.
---
lib/fflush.c | 117 +++++++++++++++++++++++++++++-----------------------------
1 files changed, 58 insertions(+), 59 deletions(-)
diff --git a/lib/fflush.c b/lib/fflush.c
index 1292a1b..9f75ccd 100644
--- a/lib/fflush.c
+++ b/lib/fflush.c
@@ -102,9 +102,6 @@ update_fpos_cache (FILE *fp, off_t pos)
int
rpl_fflush (FILE *stream)
{
- int result;
- off_t pos;
-
/* When stream is NULL, POSIX and C99 only require flushing of "output
streams and update streams in which the most recent operation was not
input", and all implementations do this.
@@ -134,72 +131,74 @@ rpl_fflush (FILE *stream)
return fflush (stream);
#else
-
- /* Notes about the file-position indicator:
- 1) The file position indicator is incremented by fgetc() and decremented
- by ungetc():
- <http://www.opengroup.org/susv3/functions/fgetc.html>
- "... the fgetc() function shall ... advance the associated file
- position indicator for the stream ..."
- <http://www.opengroup.org/susv3/functions/ungetc.html>
- "The file-position indicator is decremented by each successful
- call to ungetc()..."
- 2) <http://www.opengroup.org/susv3/functions/ungetc.html> says:
- "The value of the file-position indicator for the stream after
- reading or discarding all pushed-back bytes shall be the same
- as it was before the bytes were pushed back."
- Here we are discarding all pushed-back bytes. But more specifically,
- 3) <http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt> says:
- "[After fflush(),] the file offset of the underlying open file
- description shall be set to the file position of the stream, and
- any characters pushed back onto the stream by ungetc() ... shall
- be discarded." */
-
- /* POSIX does not specify fflush behavior for non-seekable input
- streams. Some implementations purge unread data, some return
- EBADF, some do nothing. */
- pos = ftello (stream);
- if (pos == -1)
+ {
+ /* Notes about the file-position indicator:
+ 1) The file position indicator is incremented by fgetc() and decremented
+ by ungetc():
+ <http://www.opengroup.org/susv3/functions/fgetc.html>
+ "... the fgetc() function shall ... advance the associated file
+ position indicator for the stream ..."
+ <http://www.opengroup.org/susv3/functions/ungetc.html>
+ "The file-position indicator is decremented by each successful
+ call to ungetc()..."
+ 2) <http://www.opengroup.org/susv3/functions/ungetc.html> says:
+ "The value of the file-position indicator for the stream after
+ reading or discarding all pushed-back bytes shall be the same
+ as it was before the bytes were pushed back."
+ Here we are discarding all pushed-back bytes. But more specifically,
+ 3) <http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt> says:
+ "[After fflush(),] the file offset of the underlying open file
+ description shall be set to the file position of the stream, and
+ any characters pushed back onto the stream by ungetc() ... shall
+ be discarded." */
+
+ /* POSIX does not specify fflush behavior for non-seekable input
+ streams. Some implementations purge unread data, some return
+ EBADF, some do nothing. */
+ off_t pos = ftello (stream);
+ if (pos == -1)
+ {
+ errno = EBADF;
+ return EOF;
+ }
+
+ /* Clear the ungetc buffer. */
+ clear_ungetc_buffer (stream);
+
+ /* To get here, we must be flushing a seekable input stream, so the
+ semantics of fpurge are now appropriate to clear the buffer. To
+ avoid losing data, the lseek is also necessary. */
{
- errno = EBADF;
- return EOF;
+ int result = fpurge (stream);
+ if (result != 0)
+ return result;
}
- /* Clear the ungetc buffer. */
- clear_ungetc_buffer (stream);
-
- /* To get here, we must be flushing a seekable input stream, so the
- semantics of fpurge are now appropriate to clear the buffer. To
- avoid losing data, the lseek is also necessary. */
- result = fpurge (stream);
- if (result != 0)
- return result;
-
# if (defined __sferror || defined __DragonFly__) && defined __SNPT /*
FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
- {
- /* Disable seek optimization for the next fseeko call. This tells the
- following fseeko call to seek to the desired position directly, rather
- than to seek to a block-aligned boundary. */
- int saved_flags = disable_seek_optimization (stream);
-
- result = fseeko (stream, pos, SEEK_SET);
-
- restore_seek_optimization (stream, saved_flags);
- }
- return result;
+ {
+ /* Disable seek optimization for the next fseeko call. This tells the
+ following fseeko call to seek to the desired position directly, rather
+ than to seek to a block-aligned boundary. */
+ int saved_flags = disable_seek_optimization (stream);
+ int result = fseeko (stream, pos, SEEK_SET);
+
+ restore_seek_optimization (stream, saved_flags);
+ return result;
+ }
# else
- pos = lseek (fileno (stream), pos, SEEK_SET);
- if (pos == -1)
- return EOF;
- /* After a successful lseek, update the file descriptor's position cache
- in the stream. */
- update_fpos_cache (stream, pos);
+ pos = lseek (fileno (stream), pos, SEEK_SET);
+ if (pos == -1)
+ return EOF;
+ /* After a successful lseek, update the file descriptor's position cache
+ in the stream. */
+ update_fpos_cache (stream, pos);
- return 0;
+ return 0;
# endif
+ }
#endif
}
--
1.6.1.1.347.g3f81d