On Tue, 30 Apr 2024, Jakub Jelinek wrote:
> Hi!
>
> Seems when Martin S. implemented this, he coded there strict reading
> of the standard, which said that %lc with (wint_t) 0 argument is handled
> as wchar_t[2] temp = { arg, 0 }; %ls with temp arg and so shouldn't print
> any values. But, most of the libc implementations actually handled that
> case like %c with '\0' argument, adding a single NUL character, the only
> known exception is musl.
> Recently, C23 changed this in response to GB-141 and POSIX in
> https://austingroupbugs.net/view.php?id=1647
> so that it should have the same behavior as %c with '\0'.
>
> Because there is implementation divergence, the following patch uses
> a range rather than hardcoding it to all 1s (i.e. the %c behavior),
> though the likely case is still 1 (forward looking plus most of
> implementations).
> The res.knownrange = true; assignment removed is redundant due to
> the same assignment done unconditionally before the if statement,
> rest is formatting fixes.
>
> I don't think the min >= 0 && min < 128 case is right either, I'd think
> it should be min >= 0 && max < 128, otherwise it is just some possible
> inputs are (maybe) ASCII and there can be others, but this code is a total
> mess anyway, with the min, max, likely (somewhere in [min, max]?) and then
> unlikely possibly larger than max, dunno, perhaps for at least some chars
> in the ASCII range the likely case could be for the ascii case; so perhaps
> just the one_2_one_ascii shouldn't set max to 1 and mayfail should be true
> for max >= 128. Anyway, didn't feel I should touch that right now.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK for trunk.
> Shall it go to 14.1, or wait for 14.2?
I think this can wait for 14.2.
Richard.
> 2024-04-30 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/114876
> * gimple-ssa-sprintf.cc (format_character): For min == 0 && max == 0,
> set max, likely and unlikely members to 1 rather than 0. Remove
> useless res.knownrange = true;. Formatting fixes.
>
> * gcc.dg/pr114876.c: New test.
> * gcc.dg/tree-ssa/builtin-sprintf-warn-1.c: Adjust expected
> diagnostics.
>
> --- gcc/gimple-ssa-sprintf.cc.jj 2024-01-03 11:51:22.225860346 +0100
> +++ gcc/gimple-ssa-sprintf.cc 2024-04-29 12:52:59.760668894 +0200
> @@ -2177,8 +2177,7 @@ format_character (const directive &dir,
>
> res.knownrange = true;
>
> - if (dir.specifier == 'C'
> - || dir.modifier == FMT_LEN_l)
> + if (dir.specifier == 'C' || dir.modifier == FMT_LEN_l)
> {
> /* A wide character can result in as few as zero bytes. */
> res.range.min = 0;
> @@ -2189,10 +2188,13 @@ format_character (const directive &dir,
> {
> if (min == 0 && max == 0)
> {
> - /* The NUL wide character results in no bytes. */
> - res.range.max = 0;
> - res.range.likely = 0;
> - res.range.unlikely = 0;
> + /* In strict reading of older ISO C or POSIX, this required
> + no characters to be emitted. ISO C23 changes that, so
> + does POSIX, to match what has been implemented in most of the
> + implementations, namely emitting a single NUL character.
> + Let's use 0 for minimum and 1 for all the other values. */
> + res.range.max = 1;
> + res.range.likely = res.range.unlikely = 1;
> }
> else if (min >= 0 && min < 128)
> {
> @@ -2200,11 +2202,12 @@ format_character (const directive &dir,
> is not a 1-to-1 mapping to the source character set or
> if the source set is not ASCII. */
> bool one_2_one_ascii
> - = (target_to_host_charmap[0] == 1 && target_to_host ('a') ==
> 97);
> + = (target_to_host_charmap[0] == 1
> + && target_to_host ('a') == 97);
>
> /* A wide character in the ASCII range most likely results
> in a single byte, and only unlikely in up to MB_LEN_MAX. */
> - res.range.max = one_2_one_ascii ? 1 : target_mb_len_max ();;
> + res.range.max = one_2_one_ascii ? 1 : target_mb_len_max ();
> res.range.likely = 1;
> res.range.unlikely = target_mb_len_max ();
> res.mayfail = !one_2_one_ascii;
> @@ -2235,7 +2238,6 @@ format_character (const directive &dir,
> /* A plain '%c' directive. Its output is exactly 1. */
> res.range.min = res.range.max = 1;
> res.range.likely = res.range.unlikely = 1;
> - res.knownrange = true;
> }
>
> /* Bump up the byte counters if WIDTH is greater. */
> --- gcc/testsuite/gcc.dg/pr114876.c.jj 2024-04-29 12:26:45.774965158
> +0200
> +++ gcc/testsuite/gcc.dg/pr114876.c 2024-04-29 12:51:37.863777055 +0200
> @@ -0,0 +1,34 @@
> +/* PR tree-optimization/114876 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +/* { dg-final { scan-tree-dump-not "return \[01\];" "optimized" } } */
> +/* { dg-final { scan-tree-dump "return 3;" "optimized" } } */
> +/* { dg-final { scan-tree-dump "return 4;" "optimized" } } */
> +
> +int
> +foo (void)
> +{
> + char buf[64];
> + return __builtin_sprintf (buf, "%lc%lc%lc", (__WINT_TYPE__) 0,
> (__WINT_TYPE__) 0, (__WINT_TYPE__) 0);
> +}
> +
> +int
> +bar (void)
> +{
> + char buf[64];
> + return __builtin_sprintf (buf, "%c%c%c", 0, 0, 0);
> +}
> +
> +int
> +baz (void)
> +{
> + char buf[64];
> + return __builtin_sprintf (buf, "%lc%lc%lca", (__WINT_TYPE__) 0,
> (__WINT_TYPE__) 0, (__WINT_TYPE__) 0);
> +}
> +
> +int
> +qux (void)
> +{
> + char buf[64];
> + return __builtin_sprintf (buf, "%c%c%ca", 0, 0, 0);
> +}
> --- gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-1.c.jj 2020-12-03
> 10:04:35.888092988 +0100
> +++ gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-1.c 2024-04-29
> 12:49:14.452717581 +0200
> @@ -200,11 +200,11 @@ void test_sprintf_chk_c_const (void)
> T (3, "%c%c", '1', '2');
>
> /* Wide characters. */
> - T (0, "%lc", (wint_t)0); /* { dg-warning "nul past the end" } */
> - T (1, "%lc", (wint_t)0);
> - T (1, "%lc%lc", (wint_t)0, (wint_t)0);
> + T (0, "%lc", (wint_t)0); /* { dg-warning ".%lc. directive writing up
> to 1 bytes into a region of size 0" } */
> + T (1, "%lc", (wint_t)0); /* { dg-warning "nul past the end" } */
> + T (1, "%lc%lc", (wint_t)0, (wint_t)0); /* { dg-warning ".%lc. directive
> writing up to 1 bytes into a region of size between 0 and 1" } */
> T (2, "%lc", (wint_t)0);
> - T (2, "%lc%lc", (wint_t)0, (wint_t)0);
> + T (2, "%lc%lc", (wint_t)0, (wint_t)0); /* { dg-warning "nul past the
> end" } */
>
> /* The following could result in as few as no bytes and in as many as
> MB_CUR_MAX, but since the MB_CUR_MAX value is a runtime property
> @@ -1550,7 +1550,7 @@ void test_snprintf_c_const (char *d)
>
> /* Wide characters. */
> T (0, "%lc", (wint_t)0);
> - T (1, "%lc", (wint_t)0);
> + T (1, "%lc", (wint_t)0); /* { dg-warning "output may be truncated
> before the last format character" } */
> T (2, "%lc", (wint_t)0);
>
> /* The following could result in as few as a single byte and in as many
> @@ -1603,7 +1603,7 @@ void test_snprintf_chk_c_const (void)
>
> /* Wide characters. */
> T (0, "%lc", (wint_t)0);
> - T (1, "%lc", (wint_t)0);
> + T (1, "%lc", (wint_t)0); /* { dg-warning "output may be truncated
> before the last format character" } */
> T (2, "%lc", (wint_t)0);
>
> /* The following could result in as few as a single byte and in as many
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
