Re: [PING 3] [PATCH] Less warnings for parameters declared as arrays [PR98541, PR98536]
On Mon, 31 Jul 2023, Martin Uecker via Gcc-patches wrote: > Joseph, I would appreciate if you could take a look at this? > > This fixes the remaining issues which requires me to turn the > warnings off with -Wno-vla-parameter and -Wno-nonnull in my > projects. The front-end changes are OK. -- Joseph S. Myers jos...@codesourcery.com
[PING 3] [PATCH] Less warnings for parameters declared as arrays [PR98541, PR98536]
Joseph, I would appreciate if you could take a look at this?
This fixes the remaining issues which requires me to turn the
warnings off with -Wno-vla-parameter and -Wno-nonnull in my
projects.
Am Montag, dem 03.04.2023 um 21:34 +0200 schrieb Martin Uecker:
>
> With the relatively new warnings (11..) affecting VLA bounds,
> I now get a lot of false positives with -Wall. In general, I find
> the new warnings very useful, but they seem a bit too
> aggressive and some minor tweaks are needed, otherwise they are
> too noisy. This patch suggests two changes:
>
> 1. For VLA bounds non-null is implied only when 'static' is
> used (similar to clang) and not already when a bound > 0 is
> specified:
>
> int foo(int n, char buf[static n]);
>
> int foo(10, 0); // warning with 'static' but not without.
>
>
> (It also seems problematic to require a size of 0 to indicate
> that the pointer may be null, because 0 is not allowed in
> ISO C as a size. It is also inconsistent to how arrays with
> static bound behave.)
>
> There seems to be agreement about this change in PR98541.
>
>
> 2. GCC always warns when the number of unspecified
> bounds is different between two declarations:
>
> int foo(int n, char buf[*]);
> int foo(int n, char buf[n]);
>
> or
>
> int foo(int n, char buf[n]);
> int foo(int n, char buf[*]);
>
> But the first version is useful if the size expression
> can not be specified in a header (e.g. because it uses
> a macro or variable not available there) and there is
> currently no easy way to avoid this. The warning for
> both cases was by design, but I suggest to limit the
> warning to the second case.
>
> Note that the logic currently applied by GCC is too
> simplistic anyway, as GCC does not warn for
>
> int foo(int x, int y, double m[*][y]);
> int foo(int x, int y, double m[x][*]);
>
> because the number of specified / unspecified bounds
> is the same. So I suggest to go with the attached
> patch now and add more precise warnings later
> if there is more experience with these warning
> in gernal and if this then still seems desirable.
>
>
> Martin
>
>
> Less warnings for parameters declared as arrays [PR98541, PR98536]
>
> To avoid false positivies, tune the warnings for parameters declared
> as arrays with size expressions. Only warn about null arguments with
> 'static'. Also do not warn when more bounds are specified in the new
> declaration than before.
>
> PR c/98541
> PR c/98536
>
> c-family/
> * c-warn.cc (warn_parm_array_mismatch): Do not warn if more
> bounds are specified.
>
> gcc/
> * gimple-ssa-warn-access.cc
> (pass_waccess::maybe_check_access_sizes): For VLA bounds
> in parameters, only warn about null pointers with 'static'.
>
> gcc/testsuite:
> * gcc.dg/Wnonnull-4: Adapt test.
> * gcc.dg/Wstringop-overflow-40.c: Adapt test.
> * gcc.dg/Wvla-parameter-4.c: Adapt test.
> * gcc.dg/attr-access-2.c: Adapt test.
>
>
> diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
> index 9ac43a1af6e..f79fb876142 100644
> --- a/gcc/c-family/c-warn.cc
> +++ b/gcc/c-family/c-warn.cc
> @@ -3599,23 +3599,13 @@ warn_parm_array_mismatch (location_t origloc, tree
> fndecl, tree newparms)
> continue;
> }
>
> - if (newunspec != curunspec)
> + if (newunspec > curunspec)
> {
> location_t warnloc = newloc, noteloc = origloc;
> const char *warnparmstr = newparmstr.c_str ();
> const char *noteparmstr = curparmstr.c_str ();
> unsigned warnunspec = newunspec, noteunspec = curunspec;
>
> - if (newunspec < curunspec)
> - {
> - /* If the new declaration has fewer unspecified bounds
> - point the warning to the previous declaration to make
> - it clear that that's the one to change. Otherwise,
> - point it to the new decl. */
> - std::swap (warnloc, noteloc);
> - std::swap (warnparmstr, noteparmstr);
> - std::swap (warnunspec, noteunspec);
> - }
> if (warning_n (warnloc, OPT_Wvla_parameter, warnunspec,
>"argument %u of type %s declared with "
>"%u unspecified variable bound",
> @@ -3641,16 +3631,11 @@ warn_parm_array_mismatch (location_t origloc, tree
> fndecl, tree newparms)
> continue;
> }
> }
> -
>/* Iterate over the lists of VLA variable bounds, comparing each
> - pair for equality, and diagnosing mismatches. The case of
> - the lists having different lengths is handled above so at
> - this point they do . */
> - for (tree newvbl = newa->size, curvbl = cura->size; newvbl;
> + pair for equality, and dia
[PING 2] [PATCH] Less warnings for parameters declared as arrays [PR98541, PR98536]
Ok for gcc-14 now? Am Dienstag, dem 04.04.2023 um 19:31 -0600 schrieb Jeff Law: > > > On 4/3/23 13:34, Martin Uecker via Gcc-patches wrote: > > > > > > With the relatively new warnings (11..) affecting VLA bounds, > > I now get a lot of false positives with -Wall. In general, I find > > the new warnings very useful, but they seem a bit too > > aggressive and some minor tweaks are needed, otherwise they are > > too noisy. This patch suggests two changes: > > > > 1. For VLA bounds non-null is implied only when 'static' is > > used (similar to clang) and not already when a bound > 0 is > > specified: > > > > int foo(int n, char buf[static n]); > > > > int foo(10, 0); // warning with 'static' but not without. > > > > > > (It also seems problematic to require a size of 0 to indicate > > that the pointer may be null, because 0 is not allowed in > > ISO C as a size. It is also inconsistent to how arrays with > > static bound behave.) > > > > There seems to be agreement about this change in PR98541. > > > > > > 2. GCC always warns when the number of unspecified > > bounds is different between two declarations: > > > > int foo(int n, char buf[*]); > > int foo(int n, char buf[n]); > > > > or > > > > int foo(int n, char buf[n]); > > int foo(int n, char buf[*]); > > > > But the first version is useful if the size expression > > can not be specified in a header (e.g. because it uses > > a macro or variable not available there) and there is > > currently no easy way to avoid this. The warning for > > both cases was by design, but I suggest to limit the > > warning to the second case. > > > > Note that the logic currently applied by GCC is too > > simplistic anyway, as GCC does not warn for > > > > int foo(int x, int y, double m[*][y]); > > int foo(int x, int y, double m[x][*]); > > > > because the number of specified / unspecified bounds > > is the same. So I suggest to go with the attached > > patch now and add more precise warnings later > > if there is more experience with these warning > > in gernal and if this then still seems desirable. > > > > > > Martin > > > > > > Less warnings for parameters declared as arrays [PR98541, > > PR98536] > > > > To avoid false positivies, tune the warnings for parameters > > declared > > as arrays with size expressions. Only warn about null > > arguments with > > 'static'. Also do not warn when more bounds are specified in > > the new > > declaration than before. > > > > PR c/98541 > > PR c/98536 > > > > c-family/ > > * c-warn.cc (warn_parm_array_mismatch): Do not warn if > > more > > bounds are specified. > > > > gcc/ > > * gimple-ssa-warn-access.cc > > (pass_waccess::maybe_check_access_sizes): For VLA > > bounds > > in parameters, only warn about null pointers with > > 'static'. > > > > gcc/testsuite: > > * gcc.dg/Wnonnull-4: Adapt test. > > * gcc.dg/Wstringop-overflow-40.c: Adapt test. > > * gcc.dg/Wvla-parameter-4.c: Adapt test. > > * gcc.dg/attr-access-2.c: Adapt test. > Neither appears to be a regression. Seems like it should defer to > gcc-14. > jeff
Re: [PATCH] Less warnings for parameters declared as arrays [PR98541, PR98536]
Am Dienstag, dem 04.04.2023 um 19:31 -0600 schrieb Jeff Law: > > On 4/3/23 13:34, Martin Uecker via Gcc-patches wrote: > > > > > > With the relatively new warnings (11..) affecting VLA bounds, > > I now get a lot of false positives with -Wall. In general, I find > > the new warnings very useful, but they seem a bit too > > aggressive and some minor tweaks are needed, otherwise they are > > too noisy. This patch suggests two changes: > > > > 1. For VLA bounds non-null is implied only when 'static' is > > used (similar to clang) and not already when a bound > 0 is > > specified: > > > > int foo(int n, char buf[static n]); > > > > int foo(10, 0); // warning with 'static' but not without. > > > > > > (It also seems problematic to require a size of 0 to indicate > > that the pointer may be null, because 0 is not allowed in > > ISO C as a size. It is also inconsistent to how arrays with > > static bound behave.) > > > > There seems to be agreement about this change in PR98541. > > > > > > 2. GCC always warns when the number of unspecified > > bounds is different between two declarations: > > > > int foo(int n, char buf[*]); > > int foo(int n, char buf[n]); > > > > or > > > > int foo(int n, char buf[n]); > > int foo(int n, char buf[*]); > > > > But the first version is useful if the size expression > > can not be specified in a header (e.g. because it uses > > a macro or variable not available there) and there is > > currently no easy way to avoid this. The warning for > > both cases was by design, but I suggest to limit the > > warning to the second case. > > > > Note that the logic currently applied by GCC is too > > simplistic anyway, as GCC does not warn for > > > > int foo(int x, int y, double m[*][y]); > > int foo(int x, int y, double m[x][*]); > > > > because the number of specified / unspecified bounds > > is the same. So I suggest to go with the attached > > patch now and add more precise warnings later > > if there is more experience with these warning > > in gernal and if this then still seems desirable. > > > > > > Martin > > > > > > Less warnings for parameters declared as arrays [PR98541, PR98536] > > > > > > > > > > To avoid false positivies, tune the warnings for parameters declared > > as arrays with size expressions. Only warn about null arguments with > > 'static'. Also do not warn when more bounds are specified in the new > > declaration than before. > > > > > > > > > > PR c/98541 > > PR c/98536 > > > > > > > > > > c-family/ > > * c-warn.cc (warn_parm_array_mismatch): Do not warn if more > > bounds are specified. > > > > > > > > > > gcc/ > > * gimple-ssa-warn-access.cc > > (pass_waccess::maybe_check_access_sizes): For VLA bounds > > in parameters, only warn about null pointers with 'static'. > > > > > > > > > > gcc/testsuite: > > * gcc.dg/Wnonnull-4: Adapt test. > > * gcc.dg/Wstringop-overflow-40.c: Adapt test. > > * gcc.dg/Wvla-parameter-4.c: Adapt test. > > * gcc.dg/attr-access-2.c: Adapt test. > Neither appears to be a regression. Seems like it should defer to gcc-14. Then ok for trunk now? Martin
Re: [PATCH] Less warnings for parameters declared as arrays [PR98541, PR98536]
Am Dienstag, dem 04.04.2023 um 19:31 -0600 schrieb Jeff Law: > > On 4/3/23 13:34, Martin Uecker via Gcc-patches wrote: > > > > > > With the relatively new warnings (11..) affecting VLA bounds, > > I now get a lot of false positives with -Wall. In general, I find > > the new warnings very useful, but they seem a bit too > > aggressive and some minor tweaks are needed, otherwise they are > > too noisy. This patch suggests two changes: > > > > 1. For VLA bounds non-null is implied only when 'static' is > > used (similar to clang) and not already when a bound > 0 is > > specified: > > > > int foo(int n, char buf[static n]); > > > > int foo(10, 0); // warning with 'static' but not without. > > > > > > (It also seems problematic to require a size of 0 to indicate > > that the pointer may be null, because 0 is not allowed in > > ISO C as a size. It is also inconsistent to how arrays with > > static bound behave.) > > > > There seems to be agreement about this change in PR98541. > > > > > > 2. GCC always warns when the number of unspecified > > bounds is different between two declarations: > > > > int foo(int n, char buf[*]); > > int foo(int n, char buf[n]); > > > > or > > > > int foo(int n, char buf[n]); > > int foo(int n, char buf[*]); > > > > But the first version is useful if the size expression > > can not be specified in a header (e.g. because it uses > > a macro or variable not available there) and there is > > currently no easy way to avoid this. The warning for > > both cases was by design, but I suggest to limit the > > warning to the second case. > > > > Note that the logic currently applied by GCC is too > > simplistic anyway, as GCC does not warn for > > > > int foo(int x, int y, double m[*][y]); > > int foo(int x, int y, double m[x][*]); > > > > because the number of specified / unspecified bounds > > is the same. So I suggest to go with the attached > > patch now and add more precise warnings later > > if there is more experience with these warning > > in gernal and if this then still seems desirable. > > > > > > Martin > > > > > > Less warnings for parameters declared as arrays [PR98541, PR98536] > > > > > > > > > > > > > > > > > > To avoid false positivies, tune the warnings for parameters declared > > as arrays with size expressions. Only warn about null arguments with > > 'static'. Also do not warn when more bounds are specified in the new > > declaration than before. > > > > > > > > > > > > > > > > > > PR c/98541 > > PR c/98536 > > > > > > > > > > > > > > > > > > c-family/ > > * c-warn.cc (warn_parm_array_mismatch): Do not warn if more > > bounds are specified. > > > > > > > > > > > > > > > > > > gcc/ > > * gimple-ssa-warn-access.cc > > (pass_waccess::maybe_check_access_sizes): For VLA bounds > > in parameters, only warn about null pointers with 'static'. > > > > > > > > > > > > > > > > > > gcc/testsuite: > > * gcc.dg/Wnonnull-4: Adapt test. > > * gcc.dg/Wstringop-overflow-40.c: Adapt test. > > * gcc.dg/Wvla-parameter-4.c: Adapt test. > > * gcc.dg/attr-access-2.c: Adapt test. > Neither appears to be a regression. Seems like it should defer to gcc-14. The false positives are a regression relative to earlier version of GCC because the warnings are completely new (since GCC 11). I could bring this back later, but this means there is another version of GCC where one might need to turn off these warnings. My concern is also that an otherwise very useful feature that brings some safety benefits gets underused. Martin
Re: [PATCH] Less warnings for parameters declared as arrays [PR98541, PR98536]
On 4/3/23 13:34, Martin Uecker via Gcc-patches wrote: With the relatively new warnings (11..) affecting VLA bounds, I now get a lot of false positives with -Wall. In general, I find the new warnings very useful, but they seem a bit too aggressive and some minor tweaks are needed, otherwise they are too noisy. This patch suggests two changes: 1. For VLA bounds non-null is implied only when 'static' is used (similar to clang) and not already when a bound > 0 is specified: int foo(int n, char buf[static n]); int foo(10, 0); // warning with 'static' but not without. (It also seems problematic to require a size of 0 to indicate that the pointer may be null, because 0 is not allowed in ISO C as a size. It is also inconsistent to how arrays with static bound behave.) There seems to be agreement about this change in PR98541. 2. GCC always warns when the number of unspecified bounds is different between two declarations: int foo(int n, char buf[*]); int foo(int n, char buf[n]); or int foo(int n, char buf[n]); int foo(int n, char buf[*]); But the first version is useful if the size expression can not be specified in a header (e.g. because it uses a macro or variable not available there) and there is currently no easy way to avoid this. The warning for both cases was by design, but I suggest to limit the warning to the second case. Note that the logic currently applied by GCC is too simplistic anyway, as GCC does not warn for int foo(int x, int y, double m[*][y]); int foo(int x, int y, double m[x][*]); because the number of specified / unspecified bounds is the same. So I suggest to go with the attached patch now and add more precise warnings later if there is more experience with these warning in gernal and if this then still seems desirable. Martin Less warnings for parameters declared as arrays [PR98541, PR98536] To avoid false positivies, tune the warnings for parameters declared as arrays with size expressions. Only warn about null arguments with 'static'. Also do not warn when more bounds are specified in the new declaration than before. PR c/98541 PR c/98536 c-family/ * c-warn.cc (warn_parm_array_mismatch): Do not warn if more bounds are specified. gcc/ * gimple-ssa-warn-access.cc (pass_waccess::maybe_check_access_sizes): For VLA bounds in parameters, only warn about null pointers with 'static'. gcc/testsuite: * gcc.dg/Wnonnull-4: Adapt test. * gcc.dg/Wstringop-overflow-40.c: Adapt test. * gcc.dg/Wvla-parameter-4.c: Adapt test. * gcc.dg/attr-access-2.c: Adapt test. Neither appears to be a regression. Seems like it should defer to gcc-14. jeff
[PATCH] Less warnings for parameters declared as arrays [PR98541, PR98536]
With the relatively new warnings (11..) affecting VLA bounds,
I now get a lot of false positives with -Wall. In general, I find
the new warnings very useful, but they seem a bit too
aggressive and some minor tweaks are needed, otherwise they are
too noisy. This patch suggests two changes:
1. For VLA bounds non-null is implied only when 'static' is
used (similar to clang) and not already when a bound > 0 is
specified:
int foo(int n, char buf[static n]);
int foo(10, 0); // warning with 'static' but not without.
(It also seems problematic to require a size of 0 to indicate
that the pointer may be null, because 0 is not allowed in
ISO C as a size. It is also inconsistent to how arrays with
static bound behave.)
There seems to be agreement about this change in PR98541.
2. GCC always warns when the number of unspecified
bounds is different between two declarations:
int foo(int n, char buf[*]);
int foo(int n, char buf[n]);
or
int foo(int n, char buf[n]);
int foo(int n, char buf[*]);
But the first version is useful if the size expression
can not be specified in a header (e.g. because it uses
a macro or variable not available there) and there is
currently no easy way to avoid this. The warning for
both cases was by design, but I suggest to limit the
warning to the second case.
Note that the logic currently applied by GCC is too
simplistic anyway, as GCC does not warn for
int foo(int x, int y, double m[*][y]);
int foo(int x, int y, double m[x][*]);
because the number of specified / unspecified bounds
is the same. So I suggest to go with the attached
patch now and add more precise warnings later
if there is more experience with these warning
in gernal and if this then still seems desirable.
Martin
Less warnings for parameters declared as arrays [PR98541, PR98536]
To avoid false positivies, tune the warnings for parameters declared
as arrays with size expressions. Only warn about null arguments with
'static'. Also do not warn when more bounds are specified in the new
declaration than before.
PR c/98541
PR c/98536
c-family/
* c-warn.cc (warn_parm_array_mismatch): Do not warn if more
bounds are specified.
gcc/
* gimple-ssa-warn-access.cc
(pass_waccess::maybe_check_access_sizes): For VLA bounds
in parameters, only warn about null pointers with 'static'.
gcc/testsuite:
* gcc.dg/Wnonnull-4: Adapt test.
* gcc.dg/Wstringop-overflow-40.c: Adapt test.
* gcc.dg/Wvla-parameter-4.c: Adapt test.
* gcc.dg/attr-access-2.c: Adapt test.
diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index 9ac43a1af6e..f79fb876142 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -3599,23 +3599,13 @@ warn_parm_array_mismatch (location_t origloc, tree
fndecl, tree newparms)
continue;
}
- if (newunspec != curunspec)
+ if (newunspec > curunspec)
{
location_t warnloc = newloc, noteloc = origloc;
const char *warnparmstr = newparmstr.c_str ();
const char *noteparmstr = curparmstr.c_str ();
unsigned warnunspec = newunspec, noteunspec = curunspec;
- if (newunspec < curunspec)
- {
- /* If the new declaration has fewer unspecified bounds
-point the warning to the previous declaration to make
-it clear that that's the one to change. Otherwise,
-point it to the new decl. */
- std::swap (warnloc, noteloc);
- std::swap (warnparmstr, noteparmstr);
- std::swap (warnunspec, noteunspec);
- }
if (warning_n (warnloc, OPT_Wvla_parameter, warnunspec,
"argument %u of type %s declared with "
"%u unspecified variable bound",
@@ -3641,16 +3631,11 @@ warn_parm_array_mismatch (location_t origloc, tree
fndecl, tree newparms)
continue;
}
}
-
/* Iterate over the lists of VLA variable bounds, comparing each
-pair for equality, and diagnosing mismatches. The case of
-the lists having different lengths is handled above so at
-this point they do . */
- for (tree newvbl = newa->size, curvbl = cura->size; newvbl;
+pair for equality, and diagnosing mismatches. */
+ for (tree newvbl = newa->size, curvbl = cura->size; newvbl && curvbl;
newvbl = TREE_CHAIN (newvbl), curvbl = TREE_CHAIN (curvbl))
{
- gcc_assert (curvbl);
-
tree newpos = TREE_PURPOSE (newvbl);
tree curpos = TREE_PURPOSE (curvbl);
@@ -3663,7 +3648,6 @@ warn_parm_array_mismatch (location_t origloc, tree
fndecl, tree newparms)
and both are the same expression
