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Adding %destructor surprisingly enables warnings


From: Askar Safin
Subject: Adding %destructor surprisingly enables warnings
Date: Fri, 16 Nov 2018 14:23:42 +0300

Hi. I noticed strange behavior in Bison. Probably I simply don't understand 
something. Or I found a bug.
This is my input file: http://paste.debian.net/hidden/a72e301e . I process it 
using the following command line: "bison -do test.tab.cpp test.ypp".
Bison shows no warnings.
Then I add one line. This is edited file: 
http://paste.debian.net/hidden/1d8be22a . And then I process it using the same 
command line.
And I see the following warnings:

test.ypp:63.3-66.5: warning: unset value: $$ [-Wother]
   ID[id]
   ^^^^^^
test.ypp:71.3-73.5: warning: unset value: $$ [-Wother]
 | '\'' expr[e]
   ^^^^^^^^^^^^
test.ypp:71.8-11: warning: unused value: $2 [-Wother]
 | '\'' expr[e]
        ^^^^
test.ypp:78.3-80.5: warning: unset value: $$ [-Wother]
   %empty
   ^^^^^^
test.ypp:81.3-83.5: warning: unset value: $$ [-Wother]
 | expr[car] exprs[cdr]
   ^^^^^^^^^^^^^^^^^^^^
test.ypp:81.3-6: warning: unused value: $1 [-Wother]
 | expr[car] exprs[cdr]
   ^^^^
test.ypp:81.13-17: warning: unused value: $2 [-Wother]
 | expr[car] exprs[cdr]
             ^^^^^

My OS is Debian Stretch x86_64. Bison installed from Debian repo. "dpkg -l 
bison" reports "2:3.0.4.dfsg-1+b1". "bison --version" reports "3.0.4".

So, it seems that Bison for unknown reason ignores "%define parse.error 
verbose", but %destructor somehow causes Bison to actually show warnings.

==
Askar Safin
http://vk.com/safinaskar

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