[PATCH v3 07/32] elf: Disambiguate some failures in _dl_load_cache_lookup

[Florian Weimer]

* Joseph Myers:

> On Thu, 7 Dec 2023, Florian Weimer wrote:
>
>> diff --git a/elf/dl-cache.c b/elf/dl-cache.c
>> index 804bf23222..a3eb960dac 100644
>> --- a/elf/dl-cache.c
>> +++ b/elf/dl-cache.c
>> @@ -398,8 +398,8 @@ _dl_cache_libcmp (const char *p1, const char *p2)
>>     may be unmapped at any time by a completing recursive dlopen and
>>     this function must take care that it does not return references to
>>     any data in the mapping.  */
>> -char *
>> -_dl_load_cache_lookup (const char *name)
>> +bool
>> +_dl_load_cache_lookup (const char *name, char **realname)
>
> The comment above this function definition needs updating to describe the 
> new semantics for return value and result stored in *REALNAME.
>
>> -/* Look up NAME in ld.so.cache and return the file name stored there,
>> -   or null if none is found.  Caller must free returned string.  */
>> -extern char *_dl_load_cache_lookup (const char *name) attribute_hidden;
>> +/* Look up NAME in ld.so.cache.  Return false on memory allocation
>> +   failure and do not change *REALNAME.  If lookup fails, return true
>> +   and write a null pointer to *REALNAME.  If lookup suceeds, write a
>
> "succeeds"
>
>> +   copy of the full name to *REALNAME (which has to be freed by the
>> +   caller).  */
>> +bool _dl_load_cache_lookup (const char *name, char **realname)
>> +  attribute_hidden __nonnull ((1, 2)) __attribute__ ((warn_unused_result));
>
> Something like the comment here - though the two comments give different 
> information, so don't lose the extra information on the definition unless 
> you're confident it's no longer relevant.  However, the comment here 
> doesn't actually say it returns true when lookup and allocation both 
> succeed.

Carlos previously requested that comments should be on the
implementation, so I'm going to put the full details there.

Thanks,
Florian