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warning: avoid warnings about unreachable code

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Reported by Uxio Prego.
https://lists.gnu.org/archive/html/help-bison/2018-11/msg00031.html

We also need to move the unreachable 'goto' to a reachable place,
otherwise clang complains about the code being unreachable anyway.
See also https://bugs.llvm.org/show_bug.cgi?id=39736.

Interestingly, we don't have to apply that trick to
`#define YYCDEBUG if (false) std::cerr`, clang does not warn when the
code comes from macro expansion.

* configure.ac: Use -Wunreachable-code when supported.
* data/lalr1.cc, data/yacc.c: Pacify clang's warning about `if (0)`
by using a macro.
Another possibility was to move this statement to a reachable place.
* tests/actions.at, tests/c++.at: Avoid generating unreachable code.
This commit is contained in:
Akim Demaille
2018-11-22 18:03:12 +01:00
parent 660811a6c5
commit cc050fd321
6 changed files with 24 additions and 13 deletions
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8
data/lalr1.cc
View File

@@ -971,11 +971,11 @@ b4_dollar_popdef])[]dnl
| yyerrorlab -- error raised explicitly by YYERROR. |
`---------------------------------------------------*/
yyerrorlab:
/* Pacify compilers like GCC when the user code never invokes
YYERROR and the label yyerrorlab therefore never appears in user
code. */
/* Pacify compilers when the user code never invokes YYERROR and
the label yyerrorlab therefore never appears in user code. */
if (false)
goto yyerrorlab;
YYERROR;
/* Do not reclaim the symbols of the rule whose action triggered
this YYERROR. */
yypop_ (yylen);

7
data/yacc.c
View File

@@ -1777,11 +1777,10 @@ yyerrlab:
| yyerrorlab -- error raised explicitly by YYERROR. |
`---------------------------------------------------*/
yyerrorlab:
/* Pacify compilers like GCC when the user code never invokes
YYERROR and the label yyerrorlab therefore never appears in user
code. */
/* Pacify compilers when the user code never invokes YYERROR and the
label yyerrorlab therefore never appears in user code. */
if (0)
goto yyerrorlab;
YYERROR;
/* Do not reclaim the symbols of the rule whose action triggered
this YYERROR. */