Tomi Ollila <tomi.oll...@iki.fi> writes:
> On Fri, Dec 02 2022, Thomas Schneider wrote:
>
>> As per strcasestr(3) of glibc and FreeBSD, the header that defines
>> strcasestr() is string.h, not strings.h. This may cause compilation,
>> and thus detection whether an (optimised) version is available, to
>> fail even if the function is available, when implicit declaration and
>> pointer conversion do not match.
>>
>> Signed-off-by: Thomas Schneider <q...@chaotikum.eu>
>> ---
>> I discovered this when building with Clang:
>>
>> qsx@naboo ~/src/notmuch (git)-[tags/0.32.2]
>> % gcc -o /dev/null compat/have_strcasestr.c; echo $?
>> compat/have_strcasestr.c: In function ‘main’:
>> compat/have_strcasestr.c:10:13: warning: implicit declaration of function
>> ‘strcasestr’; did you mean ‘strcasecmp’? [-Wimplicit-function-declaration]
>> 10 | found = strcasestr (haystack, needle);
>> | ^~~~~~~~~~
>> | strcasecmp
>> compat/have_strcasestr.c:10:11: warning: assignment to ‘char *’ from ‘int’
>> makes pointer from integer without a cast [-Wint-conversion]
>> 10 | found = strcasestr (haystack, needle);
>> | ^
>> 0
>> qsx@naboo ~/src/notmuch (git)-[tags/0.32.2]
>> % clang -o /dev/null compat/have_strcasestr.c; echo $?
>> compat/have_strcasestr.c:10:13: warning: call to undeclared function
>> 'strcasestr'; ISO C99 and later do not support implicit function
>> declarations [-Wimplicit-function-declaration]
>> found = strcasestr (haystack, needle);
>> ^
>> compat/have_strcasestr.c:10:11: error: incompatible integer to pointer
>> conversion assigning to 'char *' from 'int' [-Wint-conversion]
>> found = strcasestr (haystack, needle);
>> ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> 1 warning and 1 error generated.
>> 1
>>
>> configure then assumes strcasestr is not available when using Clang, so it
>> builds the variant from compat/, which later fails when linking because of
>> conflicting symbols.
>>
>> On a side note, debugging was more complicated that I’m used to, e. g.,
>> autoconf’s config.log or similar output.
>>
>> ---
>> compat/have_strcasestr.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/compat/have_strcasestr.c b/compat/have_strcasestr.c
>> index 3cd1838d..d52a62ec 100644
>> --- a/compat/have_strcasestr.c
>> +++ b/compat/have_strcasestr.c
>> @@ -1,5 +1,5 @@
>> #define _GNU_SOURCE
>> -#include <strings.h>
>> +#include <string.h>
>
> Would it be better to include both strings.h and string.h, in
> case some (rare) cases it worked only when strings.h were included
> (or would that make the test fail in some cases then...?)
I don’t think it would cause any issues, but neither would I assume both
headers to be necessary somewhere. Of course I haven’t tested it on Ye
Olde Unix With Its Special Own Taste on a workstation that pales in
comparison to my calculator, then again I assume they either (a) don’t
have strcasestr() anyway, or (b) fail to support notmuch because of some
other issues.
--Thomas
> Tomi
>
>>
>> int
>> main ()
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