PERL_UNUSED_VAR(flags) is breaking on Perl 5.8.5

[mohawk2]

This is the error (which I cannot fathom, since PERL_UNUSED_VAR just does a cast):

cc -c  -I./Encode -D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -Werror=declaration-after-statement -Wpointer-sign -O2   -DVERSION=\"2.95\" -DXS_VERSION=\"2.95\" -fpic "-I/home/travis/perl5/perlbrew/perls/5.8.5/lib/5.8.5/x86_64-linux-thread-multi/CORE"   Encode.c
Encode.xs: In function ‘process_utf8’:
Encode.xs:536:9: error: assignment of read-only variable ‘flags’
         PERL_UNUSED_VAR(flags);
         ^
make: *** [Encode.o] Error 1

Source: https://travis-ci.org/dbsrgits/dbix-class-schema-loader/jobs/339956926#L2006

Since that macro-call was added in 6128f24#diff-6ae89a05cb477ae91e301ee737d18c4dR529, is there an argument for simply zapping that line?

[dankogai]

Considering Perl 5.8.5 is gone EOL a long ago I'm reluctant to change that. I should rather consider raising minimum perl version. FYI Perl 5.8 of travis (which is 5.8.8 to be exact) is happy.

[pali]

@khwilliamson: that is your change

[khwilliamson]

That line is only in there to silence warnings, so it could be pulled out. What's being executed here is fallback code for perls that don't have the infrastructure that the faster mechanism uses. My plan is to copy that infrastructure into Encode, so it will be fast, and more importantly, there are some security issues with previous perls that are now fixed, and so those will automatically get fixed in Encode. This could go in Devel::PPPort, but we don't know when the next release of that is going to be, since the developer has gone awol, and I think Encode is the only module that really uses this.

[khwilliamson]

What this means is that offending line is very likely to be removed 3 months or so from now in Encode

[mohawk2]

Fair enough. Until then, this is why the 5.8.5 build is failing for dbsrgits/dbix-class-schema-loader#17 (put for cross-reference). The reason why 5.8.5 is a comment "Full Test of minimum supported with threads".

[ribasushi]

@khwilliamson is it not possible to add a Perl version-predicated cpp #if guard around this line?

As it stands right now I can not do future releases of DBIx::Class ( which has an unbreakable commitment to support 5.8.3+ ) until either this is fixed, or I do weird acrobatics in my CI to gate the Encode.pm lower so the rest of the CI run can pass

5.8.7, which is also affected, is even more surprisingly-widely-used. A minimum 3 months breakage at such a low level would be very unfortunate.

[ribasushi]

@dankogai please re-open this issue based on the above

[khwilliamson]

On 02/14/2018 06:01 AM, Peter Rabbitson wrote: @khwilliamson <https://github.com/khwilliamson> is it not possible to add a Perl version-predicated cpp #if guard around this line? As it stands right now I can not do future releases of DBIx::Class ( which has an unbreakable commitment to support 5.8.3+ ) until either this is fixed, or I do weird acrobatics in my CI to gate the Encode.pm lower so the rest of the CI run can pass 5.8.7, which is also affected, is even more surprisingly-widely-used. A minimum 3 months breakage at such a low level would be very unfortunate. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#129 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAGhn_6Yo2DdWi8sT7bl6jBPenXXFUEmks5tUtkegaJpZM4SBHbJ>.

What is the first version not affected?

[pali]

@khwilliamson whole purpose of usage of that PERL_UNUSED_VAR(flags) macro is to silence gcc warning : set-but-not-used. Why is then variable flags set, but not used? Cannot be that variable fully commented or ifdef-ed on configuration where is not used? I think this is correct solution (to completely remove usage of PERL_UNUSED_VAR(flags)) and not trying to find perl version which has working PERL_UNUSED_VAR macro.

[khwilliamson]

On 02/14/2018 09:58 AM, pali wrote: @khwilliamson <https://github.com/khwilliamson> whole purpose of usage of that PERL_UNUSED_VAR(flags) macro is to silence gcc warning : set-but-not-used. Why is then variable flags set, but not used? Cannot be that variable fully commented or ifdef-ed on configuration where is not used? I think this is correct solution (to completely remove usage of PERL_UNUSED_VAR(flags)) and not trying to find perl version which has working PERL_UNUSED_VAR macro.

Well, I did find the version, 5.9.3. This fails on earlier versions only because 'flags' is declared const, and a3b680e6b77 fixed that. I see we have several choices in fixing it: 1) remove the constness of 'flags' 2) remove the line entirely, and live with the compiler warnings 3) replace the line with the current definition of PERL_UNUSED_VAR, either by #undef'ing it and redefining it, or expanding it to the void* I note that this macro is used in various places in the code; presumably this is the only current one where the argument is const. It would be best actually to put this in Devel::PPPort, but that is not an immediate solution. I'm happy to fix this, but which option to use? I'm inclined to #undef PERL_UNUSED_VAR and replace it with a better definition

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