Re: clang++ 11 compilation issues

[Florian Weimer]

* Alexandre Duret-Lutz:

> (1) lib/argmatch.h includes lib/gettext.h which fails as follows
>
>> clang++ -DHAVE_CONFIG_H -I. -I..  -I.. -I.. -I../buddy/src -I../lib -I../lib 
>>  -W -Wall -Werror -Wint-to-void-pointer-cast -Wzero-as-null-pointer-constant 
>> -Wcast-align -Wpointer-arith -Wwrite-strings -Wcast-qual -DXTSTRINGDEFINES 
>> -Wdocumentation -Wmissing-declarations -Woverloaded-virtual 
>> -Wmisleading-indentation -Wimplicit-fallthrough -Wnull-dereference 
>> -Wsuggest-override -Wpedantic -fvisibility=hidden 
>> -fvisibility-inlines-hidden -DSPOT_BUILD -std=c++17 -g -O -MT autcross.o -MD 
>> -MP -MF .deps/autcross.Tpo -c -o autcross.o autcross.cc
>> In file included from autcross.cc:34:
>> In file included from ../lib/argmatch.h:31:
>> ../lib/gettext.h:234:22: error: zero as null pointer constant 
>> [-Werror,-Wzero-as-null-pointer-constant]
>>   if (msg_ctxt_id != NULL)
>>                      ^~~~
>>                      nullptr
>> /usr/lib/llvm-11/lib/clang/11.0.1/include/stddef.h:84:18: note: expanded 
>> from macro 'NULL'
>> #    define NULL __null
>>                  ^

Would you be able to check whether __null is in the preprocessed
sources?  If it is there (and the lack of further logged expansions
suggests this), then this is a compiler bug.  __null is not zero, and
should be fine to use as a null pointer constant.  This is why NULL is
not defined as 0.

Thanks,
Florian
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