Re: [PATCH v2] pahole: fix discarded-qualifiers for strchr/strstr.

hello sir,
i will do the fix, i have some questions about the project, is it 
acceptable to use C23 standard ?,  ex: null -> nullptr, constexpr 
etc..., and i saw some goto , goto statement for control flow is error 
prone can do a change about it or it's not acceptable ?

Le 10/03/2026 à 09:56, Alan Maguire a écrit :
> On 09/03/2026 16:52, d.hourtoulle wrote:
>> From: Damien Hourtoulle <[email protected]>
>>
>> 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]>
> the changes look good, but there is an existing issue in the code that would be
> good to solve while you're in the neighbourhood I think. more below..
>
>> ---
>> Changes in v2:
>>   - In type_instance__int_value loop: update sep_mutable instead of sep
>>   - In type__find_type_enum loop: introduce char *cur to iterate through
>>     the mutable copy, so sep_mutable stays const-correct and is updated
>>     correctly on each iteration
>>
>>   btf_encoder.c |  2 +-
>>   pahole.c      | 33 ++++++++++++++++-----------------
>>   2 files changed, 17 insertions(+), 18 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..9dfeeb2 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);
>> @@ -2510,9 +2510,9 @@ 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;
>> -			sep = strchr(member_name, '.');
>> -			if (!sep)
>> +			member_name = sep_mutable + 1;
>> +			sep_mutable = strchr(member_name, '.');
>> +			if (!sep_mutable)
>>   				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;
>> @@ -3126,13 +3125,13 @@ 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);
>> +	char *cur = type_enums;
>>   
>> -	type_enum = type_enums;
>> -	*sep = '\0';
>> +	*sep_mutable = '\0';
>>   
>>   	while (1) {
>> -		te = cu__find_enumeration_by_name(cu, type_enum, NULL);
>> +		te = cu__find_enumeration_by_name(cu, cur, NULL);
>>   
>>   		if (!te)
>>   			goto out;
>> @@ -3141,10 +3140,10 @@ static int type__find_type_enum(struct type *type, struct cu *cu, const char *ty
>>   		if (ret)
>>   			goto out;
>>   
>> -		if (sep == NULL)
>> +		if (sep_mutable == NULL)
>>   			break;
>> -		type_enum = sep + 1;
>> -		sep = strchr(type_enum, '+');
>> +		cur = sep_mutable + 1;
>> +		sep_mutable = strchr(cur, '+');
>>   	}
>>   
>>   	ret = 0;
> the intent of this loop is to search through a "+" concatenated list of enum names, but the problem is
> we never nullify sep_mutable (or sep in the old code) at the end of each loop iteration. so when
> we find the enumeration by name at the top of the second iteration of the while() loop were searching
> with "second+third" rather than "second". So long story short, we need a
> 		sep_mutable = '\0';
>
> ...at the end of the while loop I think.