Re: [PATCH] c: Split -Wcalloc-transposed-args warning from -Walloc-size, -Walloc-size fixes
On Mon, 18 Dec 2023, Jakub Jelinek wrote: > Hi! > > The following patch changes -Walloc-size warning to no longer warn > about int *p = calloc (1, sizeof (int));, because as discussed earlier, > the size is IMNSHO sufficient in that case, for alloc_size with 2 > arguments warns if the product of the 2 arguments is insufficiently small. > > Also, it warns also for explicit casts of malloc/calloc etc. calls > rather than just implicit, so not just > int *p = malloc (1); > but also > int *p = (int *) malloc (1); > > It also fixes some ICEs where the code didn't verify the alloc_size > arguments properly (Walloc-size-5.c testcase ICEs with vanilla trunk). > > And lastly, it introduces a coding style warning, -Wcalloc-transposed-args > to warn for calloc (sizeof (struct S), 1) and similar calls (regardless > of what they are cast to, warning whenever first argument is sizeof and > the second is not). > > Ok for trunk if this passes bootstrap/regtest? OK. -- Joseph S. Myers jos...@codesourcery.com
Re: [PATCH] c: Split -Wcalloc-transposed-args warning from -Walloc-size, -Walloc-size fixes
Am Dienstag, dem 19.12.2023 um 12:20 -0500 schrieb Jason Merrill: > On 12/19/23 03:47, Jakub Jelinek wrote: > > On Tue, Dec 19, 2023 at 08:11:11AM +0100, Martin Uecker wrote: > > > Am Montag, dem 18.12.2023 um 20:14 +0100 schrieb Jakub Jelinek: > > > > Hi! > > > > > > > > The following patch changes -Walloc-size warning to no longer warn > > > > about int *p = calloc (1, sizeof (int));, because as discussed earlier, > > > > the size is IMNSHO sufficient in that case, for alloc_size with 2 > > > > arguments warns if the product of the 2 arguments is insufficiently > > > > small. > > > > > > > > Also, it warns also for explicit casts of malloc/calloc etc. calls > > > > rather than just implicit, so not just > > > >int *p = malloc (1); > > > > but also > > > >int *p = (int *) malloc (1); > > > > > > > > It also fixes some ICEs where the code didn't verify the alloc_size > > > > arguments properly (Walloc-size-5.c testcase ICEs with vanilla trunk). > > > > > > > > And lastly, it introduces a coding style warning, > > > > -Wcalloc-transposed-args > > > > to warn for calloc (sizeof (struct S), 1) and similar calls (regardless > > > > of what they are cast to, warning whenever first argument is sizeof and > > > > the second is not). > > > > > > I would generally see function arguments that are swapped relative > > > to the documented ABI as more than a coding style issue even in > > > cases where it can be expected to make no difference. > > > > If you have suggestions how to reword the documentation, would that be > > sufficient for you? I still don't see why given correct alignment one can't > > store struct S into sizeof (struct S) sized heap char array, > > Seems to me one can in C++, anyway. An unsigned char array can provide > storage for another type, and the call to calloc can be interpreted as > creating such an array if that gives the program defined behavior. > https://eel.is/c++draft/intro.object#def:provides_storage > https://eel.is/c++draft/intro.object#def:object,implicit_creation This is also true in C. There is nothing wrong with calloc(10, 1) allocating a char array with 10 elements and then storing a struct of size 10 in it. Martin >
Re: [PATCH] c: Split -Wcalloc-transposed-args warning from -Walloc-size, -Walloc-size fixes
On 12/19/23 03:47, Jakub Jelinek wrote: On Tue, Dec 19, 2023 at 08:11:11AM +0100, Martin Uecker wrote: Am Montag, dem 18.12.2023 um 20:14 +0100 schrieb Jakub Jelinek: Hi! The following patch changes -Walloc-size warning to no longer warn about int *p = calloc (1, sizeof (int));, because as discussed earlier, the size is IMNSHO sufficient in that case, for alloc_size with 2 arguments warns if the product of the 2 arguments is insufficiently small. Also, it warns also for explicit casts of malloc/calloc etc. calls rather than just implicit, so not just int *p = malloc (1); but also int *p = (int *) malloc (1); It also fixes some ICEs where the code didn't verify the alloc_size arguments properly (Walloc-size-5.c testcase ICEs with vanilla trunk). And lastly, it introduces a coding style warning, -Wcalloc-transposed-args to warn for calloc (sizeof (struct S), 1) and similar calls (regardless of what they are cast to, warning whenever first argument is sizeof and the second is not). I would generally see function arguments that are swapped relative to the documented ABI as more than a coding style issue even in cases where it can be expected to make no difference. If you have suggestions how to reword the documentation, would that be sufficient for you? I still don't see why given correct alignment one can't store struct S into sizeof (struct S) sized heap char array, Seems to me one can in C++, anyway. An unsigned char array can provide storage for another type, and the call to calloc can be interpreted as creating such an array if that gives the program defined behavior. https://eel.is/c++draft/intro.object#def:provides_storage https://eel.is/c++draft/intro.object#def:object,implicit_creation Jason
Re: [PATCH] c: Split -Wcalloc-transposed-args warning from -Walloc-size, -Walloc-size fixes
Am Dienstag, dem 19.12.2023 um 09:47 +0100 schrieb Jakub Jelinek: > On Tue, Dec 19, 2023 at 08:11:11AM +0100, Martin Uecker wrote: > > Am Montag, dem 18.12.2023 um 20:14 +0100 schrieb Jakub Jelinek: > > > Hi! > > > > > > The following patch changes -Walloc-size warning to no longer warn > > > about int *p = calloc (1, sizeof (int));, because as discussed earlier, > > > the size is IMNSHO sufficient in that case, for alloc_size with 2 > > > arguments warns if the product of the 2 arguments is insufficiently small. > > > > > > Also, it warns also for explicit casts of malloc/calloc etc. calls > > > rather than just implicit, so not just > > > int *p = malloc (1); > > > but also > > > int *p = (int *) malloc (1); > > > > > > It also fixes some ICEs where the code didn't verify the alloc_size > > > arguments properly (Walloc-size-5.c testcase ICEs with vanilla trunk). > > > > > > And lastly, it introduces a coding style warning, -Wcalloc-transposed-args > > > to warn for calloc (sizeof (struct S), 1) and similar calls (regardless > > > of what they are cast to, warning whenever first argument is sizeof and > > > the second is not). > > > > I would generally see function arguments that are swapped relative > > to the documented ABI as more than a coding style issue even in > > cases where it can be expected to make no difference. > > If you have suggestions how to reword the documentation, would that be > sufficient for you? Maybe simple remove "This is a coding style warning." ? > I still don't see why given correct alignment one can't > store struct S into sizeof (struct S) sized heap char array, but if the > documentation explain reasons why should one write it one way and not the > other except for coding style, sure. I do not think we need to argue one way or the other in the documentation. > > > > Ok for trunk if this passes bootstrap/regtest? > > > > I wonder whether we could turn on -Walloc-size for -Wall with this change? > > I think that is a possibility, yes. > > BTW, the patch passed bootstrap/regtest on x86_64-linux and i686-linux. > > Jakub Anyway, thank you for fixing / improving this warning! Martin
Re: [PATCH] c: Split -Wcalloc-transposed-args warning from -Walloc-size, -Walloc-size fixes
On Tue, Dec 19, 2023 at 08:11:11AM +0100, Martin Uecker wrote: > Am Montag, dem 18.12.2023 um 20:14 +0100 schrieb Jakub Jelinek: > > Hi! > > > > The following patch changes -Walloc-size warning to no longer warn > > about int *p = calloc (1, sizeof (int));, because as discussed earlier, > > the size is IMNSHO sufficient in that case, for alloc_size with 2 > > arguments warns if the product of the 2 arguments is insufficiently small. > > > > Also, it warns also for explicit casts of malloc/calloc etc. calls > > rather than just implicit, so not just > > int *p = malloc (1); > > but also > > int *p = (int *) malloc (1); > > > > It also fixes some ICEs where the code didn't verify the alloc_size > > arguments properly (Walloc-size-5.c testcase ICEs with vanilla trunk). > > > > And lastly, it introduces a coding style warning, -Wcalloc-transposed-args > > to warn for calloc (sizeof (struct S), 1) and similar calls (regardless > > of what they are cast to, warning whenever first argument is sizeof and > > the second is not). > > I would generally see function arguments that are swapped relative > to the documented ABI as more than a coding style issue even in > cases where it can be expected to make no difference. If you have suggestions how to reword the documentation, would that be sufficient for you? I still don't see why given correct alignment one can't store struct S into sizeof (struct S) sized heap char array, but if the documentation explain reasons why should one write it one way and not the other except for coding style, sure. > > Ok for trunk if this passes bootstrap/regtest? > > I wonder whether we could turn on -Walloc-size for -Wall with this change? I think that is a possibility, yes. BTW, the patch passed bootstrap/regtest on x86_64-linux and i686-linux. Jakub
Re: [PATCH] c: Split -Wcalloc-transposed-args warning from -Walloc-size, -Walloc-size fixes
Am Montag, dem 18.12.2023 um 20:14 +0100 schrieb Jakub Jelinek:
> Hi!
>
> The following patch changes -Walloc-size warning to no longer warn
> about int *p = calloc (1, sizeof (int));, because as discussed earlier,
> the size is IMNSHO sufficient in that case, for alloc_size with 2
> arguments warns if the product of the 2 arguments is insufficiently small.
>
> Also, it warns also for explicit casts of malloc/calloc etc. calls
> rather than just implicit, so not just
> int *p = malloc (1);
> but also
> int *p = (int *) malloc (1);
>
> It also fixes some ICEs where the code didn't verify the alloc_size
> arguments properly (Walloc-size-5.c testcase ICEs with vanilla trunk).
>
> And lastly, it introduces a coding style warning, -Wcalloc-transposed-args
> to warn for calloc (sizeof (struct S), 1) and similar calls (regardless
> of what they are cast to, warning whenever first argument is sizeof and
> the second is not).
I would generally see function arguments that are swapped relative
to the documented ABI as more than a coding style issue even in
cases where it can be expected to make no difference.
>
> Ok for trunk if this passes bootstrap/regtest?
I wonder whether we could turn on -Walloc-size for -Wall with this change?
Martin
>
> If yes, I'd implement it for C++ next.
> If not, we should at least fix the ICEs.
>
> 2023-12-18 Jakub Jelinek
>
> gcc/
> * doc/invoke.texi (-Walloc-size): Add to the list of
> warning options, remove unnecessary line-break.
> (-Wcalloc-transposed-args): Document new warning.
> gcc/c-family/
> * c.opt (Wcalloc-transposed-args): New warning.
> * c-common.h (warn_for_calloc, warn_for_alloc_size): Declare.
> * c-warn.cc (warn_for_calloc, warn_for_alloc_size): New functions.
> gcc/c/
> * c-parser.cc (c_parser_postfix_expression_after_primary): Grow
> sizeof_arg and sizeof_arg_loc arrays to 6 elements. Call
> warn_for_calloc if warn_calloc_transposed_args for functions with
> alloc_size type attribute with 2 arguments.
> (c_parser_expr_list): Use 6 instead of 3.
> * c-typeck.cc (build_c_cast): Call warn_for_alloc_size for casts
> of calls to functions with alloc_size type attribute.
> (convert_for_assignment): Likewise.
> gcc/testsuite/
> * gcc.dg/Walloc-size-4.c: New test.
> * gcc.dg/Walloc-size-5.c: New test.
> * gcc.dg/Wcalloc-transposed-args-1.c: New test.
>
> --- gcc/doc/invoke.texi.jj2023-12-18 09:39:49.411355496 +0100
> +++ gcc/doc/invoke.texi 2023-12-18 19:59:37.139525128 +0100
> @@ -328,7 +328,7 @@ Objective-C and Objective-C++ Dialects}.
> -pedantic-errors -fpermissive
> -w -Wextra -Wall -Wabi=@var{n}
> -Waddress -Wno-address-of-packed-member -Waggregate-return
> --Walloc-size-larger-than=@var{byte-size} -Walloc-zero
> +-Walloc-size -Walloc-size-larger-than=@var{byte-size} -Walloc-zero
> -Walloca -Walloca-larger-than=@var{byte-size}
> -Wno-aggressive-loop-optimizations
> -Warith-conversion
> @@ -344,6 +344,7 @@ Objective-C and Objective-C++ Dialects}.
> -Wc++20-compat
> -Wno-c++11-extensions -Wno-c++14-extensions -Wno-c++17-extensions
> -Wno-c++20-extensions -Wno-c++23-extensions
> +-Wcalloc-transposed-args
> -Wcast-align -Wcast-align=strict -Wcast-function-type -Wcast-qual
> -Wchar-subscripts
> -Wclobbered -Wcomment
> @@ -8260,8 +8261,7 @@ Warn about calls to allocation functions
> @code{alloc_size} that specify insufficient size for the target type of
> the pointer the result is assigned to, including those to the built-in
> forms of the functions @code{aligned_alloc}, @code{alloca},
> -@code{calloc},
> -@code{malloc}, and @code{realloc}.
> +@code{calloc}, @code{malloc}, and @code{realloc}.
>
> @opindex Wno-alloc-zero
> @opindex Walloc-zero
> @@ -8274,6 +8274,21 @@ when called with a zero size differs amo
> of @code{realloc} has been deprecated) relying on it may result in subtle
> portability bugs and should be avoided.
>
> +@opindex Wcalloc-transposed-args
> +@opindex Wno-calloc-transposed-args
> +@item -Wcalloc-transposed-args
> +Warn about calls to allocation functions decorated with attribute
> +@code{alloc_size} with two arguments, which use @code{sizeof} operator
> +as the earlier size argument and don't use it as the later size argument.
> +This is a coding style warning. The first argument to @code{calloc} is
> +documented to be number of elements in array, while the second argument
> +is size of each element, so @code{calloc (@var{n}, sizeof (int))} is
> preferred
> +over @code{calloc (sizeof (int), @var{n})}. If @code{sizeof} in the earlier
> +argument and not the latter is intentional, the warning can be suppressed
> +by using @code{calloc (sizeof (struct @var{S}) + 0, n)} or
> +@code{calloc (1 * sizeof (struct @var{S}), 4)} or using @code{sizeof} in the
> +later argument as well.
> +
> @opindex Walloc-size-larger-than=
> @opindex Wno-alloc-size-larger-than
> @item
[PATCH] c: Split -Wcalloc-transposed-args warning from -Walloc-size, -Walloc-size fixes
Hi!
The following patch changes -Walloc-size warning to no longer warn
about int *p = calloc (1, sizeof (int));, because as discussed earlier,
the size is IMNSHO sufficient in that case, for alloc_size with 2
arguments warns if the product of the 2 arguments is insufficiently small.
Also, it warns also for explicit casts of malloc/calloc etc. calls
rather than just implicit, so not just
int *p = malloc (1);
but also
int *p = (int *) malloc (1);
It also fixes some ICEs where the code didn't verify the alloc_size
arguments properly (Walloc-size-5.c testcase ICEs with vanilla trunk).
And lastly, it introduces a coding style warning, -Wcalloc-transposed-args
to warn for calloc (sizeof (struct S), 1) and similar calls (regardless
of what they are cast to, warning whenever first argument is sizeof and
the second is not).
Ok for trunk if this passes bootstrap/regtest?
If yes, I'd implement it for C++ next.
If not, we should at least fix the ICEs.
2023-12-18 Jakub Jelinek
gcc/
* doc/invoke.texi (-Walloc-size): Add to the list of
warning options, remove unnecessary line-break.
(-Wcalloc-transposed-args): Document new warning.
gcc/c-family/
* c.opt (Wcalloc-transposed-args): New warning.
* c-common.h (warn_for_calloc, warn_for_alloc_size): Declare.
* c-warn.cc (warn_for_calloc, warn_for_alloc_size): New functions.
gcc/c/
* c-parser.cc (c_parser_postfix_expression_after_primary): Grow
sizeof_arg and sizeof_arg_loc arrays to 6 elements. Call
warn_for_calloc if warn_calloc_transposed_args for functions with
alloc_size type attribute with 2 arguments.
(c_parser_expr_list): Use 6 instead of 3.
* c-typeck.cc (build_c_cast): Call warn_for_alloc_size for casts
of calls to functions with alloc_size type attribute.
(convert_for_assignment): Likewise.
gcc/testsuite/
* gcc.dg/Walloc-size-4.c: New test.
* gcc.dg/Walloc-size-5.c: New test.
* gcc.dg/Wcalloc-transposed-args-1.c: New test.
--- gcc/doc/invoke.texi.jj 2023-12-18 09:39:49.411355496 +0100
+++ gcc/doc/invoke.texi 2023-12-18 19:59:37.139525128 +0100
@@ -328,7 +328,7 @@ Objective-C and Objective-C++ Dialects}.
-pedantic-errors -fpermissive
-w -Wextra -Wall -Wabi=@var{n}
-Waddress -Wno-address-of-packed-member -Waggregate-return
--Walloc-size-larger-than=@var{byte-size} -Walloc-zero
+-Walloc-size -Walloc-size-larger-than=@var{byte-size} -Walloc-zero
-Walloca -Walloca-larger-than=@var{byte-size}
-Wno-aggressive-loop-optimizations
-Warith-conversion
@@ -344,6 +344,7 @@ Objective-C and Objective-C++ Dialects}.
-Wc++20-compat
-Wno-c++11-extensions -Wno-c++14-extensions -Wno-c++17-extensions
-Wno-c++20-extensions -Wno-c++23-extensions
+-Wcalloc-transposed-args
-Wcast-align -Wcast-align=strict -Wcast-function-type -Wcast-qual
-Wchar-subscripts
-Wclobbered -Wcomment
@@ -8260,8 +8261,7 @@ Warn about calls to allocation functions
@code{alloc_size} that specify insufficient size for the target type of
the pointer the result is assigned to, including those to the built-in
forms of the functions @code{aligned_alloc}, @code{alloca},
-@code{calloc},
-@code{malloc}, and @code{realloc}.
+@code{calloc}, @code{malloc}, and @code{realloc}.
@opindex Wno-alloc-zero
@opindex Walloc-zero
@@ -8274,6 +8274,21 @@ when called with a zero size differs amo
of @code{realloc} has been deprecated) relying on it may result in subtle
portability bugs and should be avoided.
+@opindex Wcalloc-transposed-args
+@opindex Wno-calloc-transposed-args
+@item -Wcalloc-transposed-args
+Warn about calls to allocation functions decorated with attribute
+@code{alloc_size} with two arguments, which use @code{sizeof} operator
+as the earlier size argument and don't use it as the later size argument.
+This is a coding style warning. The first argument to @code{calloc} is
+documented to be number of elements in array, while the second argument
+is size of each element, so @code{calloc (@var{n}, sizeof (int))} is preferred
+over @code{calloc (sizeof (int), @var{n})}. If @code{sizeof} in the earlier
+argument and not the latter is intentional, the warning can be suppressed
+by using @code{calloc (sizeof (struct @var{S}) + 0, n)} or
+@code{calloc (1 * sizeof (struct @var{S}), 4)} or using @code{sizeof} in the
+later argument as well.
+
@opindex Walloc-size-larger-than=
@opindex Wno-alloc-size-larger-than
@item -Walloc-size-larger-than=@var{byte-size}
--- gcc/c-family/c.opt.jj 2023-12-14 07:49:52.951583511 +0100
+++ gcc/c-family/c.opt 2023-12-18 13:57:11.834184689 +0100
@@ -502,6 +502,10 @@ Wc++26-extensions
C++ ObjC++ Var(warn_cxx26_extensions) Warning Init(1)
Warn about C++26 constructs in code compiled with an older standard.
+Wcalloc-transposed-args
+C ObjC C++ ObjC++ Var(warn_calloc_transposed_args) Warning LangEnabledBy(C
ObjC C++ ObjC++,Wextra)
+Warn about suspicious calls to calloc-like functions where sizeof
