[njs] Added pkg-config-based libxml2 detection.

[Konstantin Pavlov]

Hi Alejandro,

On 30/01/2023 5:52 PM, Alejandro Colomar wrote:
> Hi Konstantin!
>
> On 1/31/23 01:52, Konstantin Pavlov wrote:
>> details: https://hg.nginx.org/njs/rev/c789bb7313d4
>> branches:
>> changeset: 2030:c789bb7313d4
>> user:      Konstantin Pavlov <thresh at nginx.com>
>> date:      Fri Jan 27 15:10:57 2023 -0800
>> description:
>> Added pkg-config-based libxml2 detection.
>>
>> diffstat:
>>
>>   auto/libxml2 |  26 +++++++++++++++++++++-----
>>   1 files changed, 21 insertions(+), 5 deletions(-)
>>
>> diffs (45 lines):
>>
>> diff -r b0f3bc578f08 -r c789bb7313d4 auto/libxml2
>> --- a/auto/libxml2    Fri Jan 27 15:08:41 2023 -0800
>> +++ b/auto/libxml2    Fri Jan 27 15:10:57 2023 -0800
>> @@ -6,12 +6,8 @@ NJS_HAVE_LIBXML2=NO
>>     if [ $NJS_LIBXML2 = YES ]; then
>>       njs_found=no
>> -
>> -    njs_feature="libxml2"
>>       njs_feature_name=NJS_HAVE_LIBXML2
>>       njs_feature_run=no
>> -    njs_feature_incs="/usr/include/libxml2"
>> -    njs_feature_libs="-lxml2"
>>       njs_feature_test="#include <libxml/parser.h>
>>                         #include <libxml/tree.h>
>>   @@ -22,7 +18,27 @@ if [ $NJS_LIBXML2 = YES ]; then
>>                             xmlCleanupParser();
>>                             return 0;
>>                         }"
>> -    . auto/feature
>> +
>> +
>> +    if /bin/sh -c "(pkg-config libxml-2.0 --exists)" >> 
>> $NJS_AUTOCONF_ERR 2>&1; then
>> +
>> +        # pkg-config
>> +
>> +        njs_feature="libxml2 via pkg-config"
>> +        njs_feature_incs=`pkg-config libxml-2.0 --cflags | sed -n -e 
>> 's/.*-I *\([^ ][^ ]*\).*/\1/p'`
>
> I think you want -‐cflags‐only‐I
> I'm not sure if it has any portability issues to old versions of 
> pkg-config maybe?

Do you mean so pkg-config only outputs -I/foo/bar but not any non-I 
parts of cflags like -Dfoo if any?  Maybe. Not sure it's a big deal though?