Bruno Haible <[EMAIL PROTECTED]> writes:
> Here the problem is:
> mbstate_t mbstate = {0};
> ISO C 99 guarantees only that mbstate_t is not an array type; it could
> be a scalar or pointer type.
But that's OK. The initializer is valid C89 (and C99) even if
mbstate_t is a scalar or pointer type. The following is standard C:
int x = { 0 };
Similarly, the following is also valid C:
mbstate_t mbstate = {0};
regardless of whether mbstate_t is a struct, or an array, or a scalar,
or a union.
Changing the code to use memset makes the code less readable and more
error-prone. Also, it has some problems on implementations where null
pointers and/or floating point values do not have all-bits-zero
representation; a problem in this area is has almost zero probability
for GNU code and mbstate_t but if it's easy to make the code portable
then we might as well do so.
This subject has come up a couple of times before. In
<http://lists.gnu.org/archive/html/bug-coreutils/2005-06/msg00156.html>
I noted that glibc now sometimes uses the following style when the
type isn't known to be a structure or a scalar:
sometype somevar = { 0, };
as an indication to the reader as to what is going on.
The question is whether we want to use this style, which I think is
nicer, or cater to "gcc -Wall" even if its warning is
counterproductive. Personally I'd rather do the former, so I'd prefer
the following patch, but it's really up to Jim.
2006-10-09 Paul Eggert <[EMAIL PROTECTED]>
* lib/quotearg.c (quotearg_buffer_restyled): Use
initializer rather than memset to initialize an object
to zero. This is easier to read and is less likely to
introduce an runtime error due to a mixup. It causes
"gcc -Wall" to issue a warning, but you can work around
this by appending -Wno-missing-braces.
* src/ls.c (quote_name): Likewise.
* src/pathchk.c (portable_chars_only): Likewise.
* src/shred.c (main): Likewise.
* src/stty.c (main): Likewise.
* src/tr.c (card_of_complement): Likewise.
* src/wc.c (wc): Likewise.
Index: lib/quotearg.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/quotearg.c,v
retrieving revision 1.50
diff -p -u -r1.50 quotearg.c
--- lib/quotearg.c 3 Oct 2006 06:33:39 -0000 1.50
+++ lib/quotearg.c 9 Oct 2006 19:14:01 -0000
@@ -415,8 +415,7 @@ quotearg_buffer_restyled (char *buffer,
}
else
{
- mbstate_t mbstate;
- memset (&mbstate, 0, sizeof mbstate);
+ mbstate_t mbstate = { 0, };
m = 0;
printable = true;
Index: src/ls.c
===================================================================
RCS file: /fetish/cu/src/ls.c,v
retrieving revision 1.442
diff -p -u -r1.442 ls.c
--- src/ls.c 3 Sep 2006 02:53:16 -0000 1.442
+++ src/ls.c 9 Oct 2006 19:14:17 -0000
@@ -3604,8 +3604,7 @@ quote_name (FILE *out, const char *name,
reach its end, replacing each non-printable multibyte
character with a single question mark. */
{
- mbstate_t mbstate;
- memset (&mbstate, 0, sizeof mbstate);
+ mbstate_t mbstate = { 0, };
do
{
wchar_t wc;
Index: src/pathchk.c
===================================================================
RCS file: /fetish/cu/src/pathchk.c,v
retrieving revision 1.89
diff -p -u -r1.89 pathchk.c
--- src/pathchk.c 9 Oct 2006 11:56:41 -0000 1.89
+++ src/pathchk.c 9 Oct 2006 19:14:19 -0000
@@ -200,11 +200,8 @@ portable_chars_only (char const *file, s
if (*invalid)
{
- mbstate_t mbstate;
- size_t charlen;
-
- memset (&mbstate, 0, sizeof mbstate);
- charlen = mbrlen (invalid, filelen - validlen, &mbstate);
+ mbstate_t mbstate = { 0, };
+ size_t charlen = mbrlen (invalid, filelen - validlen, &mbstate);
error (0, 0,
_("nonportable character %s in file name %s"),
quotearg_n_style_mem (1, locale_quoting_style, invalid,
Index: src/shred.c
===================================================================
RCS file: /fetish/cu/src/shred.c,v
retrieving revision 1.130
diff -p -u -r1.130 shred.c
--- src/shred.c 3 Sep 2006 02:53:16 -0000 1.130
+++ src/shred.c 9 Oct 2006 19:14:21 -0000
@@ -1091,7 +1091,7 @@ int
main (int argc, char **argv)
{
bool ok = true;
- struct Options flags;
+ struct Options flags = { 0, };
char **file;
int n_files;
int c;
@@ -1106,8 +1106,6 @@ main (int argc, char **argv)
atexit (close_stdout);
- memset (&flags, 0, sizeof flags);
-
flags.n_iterations = DEFAULT_PASSES;
flags.size = -1;
Index: src/stty.c
===================================================================
RCS file: /fetish/cu/src/stty.c,v
retrieving revision 1.138
diff -p -u -r1.138 stty.c
--- src/stty.c 9 Jul 2005 07:39:04 -0000 1.138
+++ src/stty.c 9 Oct 2006 19:14:23 -0000
@@ -729,7 +729,10 @@ settings, CHAR is taken literally, or co
int
main (int argc, char **argv)
{
- struct termios mode;
+ /* Initialize to all zeroes so there is no risk memcmp will report a
+ spurious difference in an uninitialized portion of the structure. */
+ struct termios mode = { 0, };
+
enum output_type output_type;
int optc;
int argi = 0;
@@ -840,9 +843,6 @@ main (int argc, char **argv)
else
device_name = _("standard input");
- /* Initialize to all zeroes so there is no risk memcmp will report a
- spurious difference in an uninitialized portion of the structure. */
- memset (&mode, 0, sizeof (mode));
if (tcgetattr (STDIN_FILENO, &mode))
error (EXIT_FAILURE, errno, "%s", device_name);
@@ -1002,7 +1002,9 @@ main (int argc, char **argv)
if (require_set_attr)
{
- struct termios new_mode;
+ /* Initialize to all zeroes so there is no risk memcmp will report a
+ spurious difference in an uninitialized portion of the structure. */
+ struct termios new_mode = { 0, };
if (tcsetattr (STDIN_FILENO, TCSADRAIN, &mode))
error (EXIT_FAILURE, errno, "%s", device_name);
@@ -1014,9 +1016,6 @@ main (int argc, char **argv)
this partial failure, get the current terminal attributes and
compare them to the requested ones. */
- /* Initialize to all zeroes so there is no risk memcmp will report a
- spurious difference in an uninitialized portion of the structure. */
- memset (&new_mode, 0, sizeof (new_mode));
if (tcgetattr (STDIN_FILENO, &new_mode))
error (EXIT_FAILURE, errno, "%s", device_name);
Index: src/tr.c
===================================================================
RCS file: /fetish/cu/src/tr.c,v
retrieving revision 1.145
diff -p -u -r1.145 tr.c
--- src/tr.c 9 Jul 2006 17:04:48 -0000 1.145
+++ src/tr.c 9 Oct 2006 19:14:24 -0000
@@ -1177,9 +1177,8 @@ card_of_complement (struct Spec_list *s)
{
int c;
int cardinality = N_CHARS;
- bool in_set[N_CHARS];
+ bool in_set[N_CHARS] = { 0, };
- memset (in_set, 0, sizeof in_set);
s->state = BEGIN_STATE;
while ((c = get_next (s, NULL)) != -1)
{
Index: src/wc.c
===================================================================
RCS file: /fetish/cu/src/wc.c,v
retrieving revision 1.112
diff -p -u -r1.112 wc.c
--- src/wc.c 21 Aug 2006 07:30:47 -0000 1.112
+++ src/wc.c 9 Oct 2006 19:14:27 -0000
@@ -273,7 +273,7 @@ wc (int fd, char const *file_x, struct f
{
bool in_word = false;
uintmax_t linepos = 0;
- mbstate_t state;
+ mbstate_t state = { 0, };
uintmax_t last_error_line = 0;
int last_error_errno = 0;
# if SUPPORT_OLD_MBRTOWC
@@ -289,7 +289,6 @@ wc (int fd, char const *file_x, struct f
const size_t prev = 0;
# endif
- memset (&state, 0, sizeof (mbstate_t));
while ((bytes_read = safe_read (fd, buf + prev, BUFFER_SIZE - prev)) > 0)
{
const char *p;
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