Re: [PATCH] pahole: fix discarded-qualifiers for strchr/strstr

On 04/03/2026 03:06, damien hourtoulle wrote:
> From fa4866e368f5131ddcf6fddccc13203fab88d00d Mon Sep 17 00:00:00 2001
> From: Damien Hourtoulle <[email protected]>
> Date: Wed, 4 Mar 2026 03:30:31 +0100
> Subject: [PATCH] pahole: fix discarded-qualifiers for strchr/strstr.
> 
> Glibc 2.43 added C23 const-preserving overloads :
> https://sourceware.org/glibc/wiki/Release/2.43.
> 
> For the function prototype__new, fix local variable declaration to use
> the correct const char* type instead of char*, removing the need to
> discard
> the const qualifier.
> 
> Signed-off-by: Damien Hourtoulle <[email protected]>

hi, there are a few issues below I think..

> ---
>  btf_encoder.c |  2 +-
>  pahole.c      | 19 +++++++++----------
>  2 files changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/btf_encoder.c b/btf_encoder.c
> index aa7cd1c..d36984a 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -1218,7 +1218,7 @@ static bool str_contains_non_fn_suffix(const char *str) {
>                 ".cold",
>                 ".part"
>         };
> -       char *suffix = strchr(str, '.');
> +       const char *suffix = strchr(str, '.');
>         int i;
> 
>         if (!suffix)
> diff --git a/pahole.c b/pahole.c
> index 02a0d19..4184703 100644
> --- a/pahole.c
> +++ b/pahole.c
> @@ -2483,7 +2483,7 @@ static int64_t type_instance__int_value(struct
> type_instance *instance, const ch
>         int byte_offset = 0;
> 
>         if (!member) {
> -               char *sep = strchr(member_name_orig, '.');
> +               const char *sep = strchr(member_name_orig, '.');
> 
>                 if (!sep)
>                         return -1;
> @@ -2496,8 +2496,8 @@ static int64_t type_instance__int_value(struct
> type_instance *instance, const ch
>                 char *member_name = member_name_alloc;
>                 struct type *type = instance->type;
> 
> -               sep = member_name_alloc + (sep - member_name_orig);
> -               *sep = 0;
> +               char *sep_mutable = member_name_alloc + (sep -
> member_name_orig);  // sep mutable for the copy
> +               *sep_mutable = 0;
> 
>                 while (1) {
>                         member = type__find_member_by_name(type, member_name);
> @@ -2510,7 +2510,7 @@ out_free_member_name:
>                         type = tag__type(cu__type(cu, member->tag.type));
>                         if (type == NULL)
>                                 goto out_free_member_name;
> -                       member_name = sep + 1;
> +                       member_name = sep_mutable + 1;
>                         sep = strchr(member_name, '.');

I think this should be

sep_mutable = strchr(member_name, '.');


>                         if (!sep)
>                                 break;
> @@ -2950,7 +2950,7 @@ static struct prototype *prototype__new(const
> char *expression)
> 
>         strcpy(prototype->name, expression);
> 
> -       const char *name = prototype->name;
> +       char *name = prototype->name;
> 
>         prototype->nr_args = 0;
> 
> @@ -2964,10 +2964,9 @@ static struct prototype *prototype__new(const
> char *expression)
>         if (args_close == NULL)
>                 goto out_no_closing_parens;
> 
> +       *args_open++ = *args_close = '\0';
>         char *args = args_open;
> 
> -       *args++ = *args_close = '\0';
> -
>         while (isspace(*args))
>                 ++args;
> 
> @@ -3114,7 +3113,7 @@ static int type__find_type_enum(struct type
> *type, struct cu *cu, const char *ty
>                 return type__add_type_enum(type, te, cu);
> 
>         // Now look at a 'virtual enum', i.e. the concatenation of
> multiple enums
> -       char *sep = strchr(type_enum, '+');
> +       const char *sep = strchr(type_enum, '+');
> 
>         if (!sep)
>                 return -1;
> @@ -3126,10 +3125,10 @@ static int type__find_type_enum(struct type
> *type, struct cu *cu, const char *ty
> 
>         int ret = -1;
> 
> -       sep = type_enums + (sep - type_enum);
> +       char *sep_mutable = type_enums + (sep - type_enum);
> 
>         type_enum = type_enums;
> -       *sep = '\0';
> +       *sep_mutable = '\0';
> 
>         while (1) {
>                 te = cu__find_enumeration_by_name(cu, type_enum, NULL);


there's a similar issue in the loop here not visible in patch diffs I think;
the loop now updates sep whereas it should update sep_mutable.