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Re: Bogus Bison 3.8.2 warning: suspicious sequence in the output
From: |
Akim Demaille |
Subject: |
Re: Bogus Bison 3.8.2 warning: suspicious sequence in the output |
Date: |
Sat, 6 Nov 2021 20:09:45 +0100 |
Hi Marko,
> Le 27 oct. 2021 à 15:04, Marko Mäkelä <marko.makela@iki.fi> a écrit :
>
> Hi,
>
> Bison 3.8.2 is issuing the following warning for a grammar whose semantic
> action includes the variable name my_charset_utf8mb4_bin:
>
> yy_mariadb.cc:35834: warning: suspicious sequence in the output: b4_bin
> [-Wother]
Bummer...
> It seems to me that the regular expression in
> http://git.savannah.gnu.org/cgit/bison.git/tree/src/scan-skel.l is too
> greedy, or the check should be suppressed if the input contains such
> identifiers.
Let's start with "too greedy". Collecting all the identifiers in the input is
too much effort for this warning.
> A quick search of the Bison Texinfo for b4_ or m4_ did not find anything.
> Because those are not documented as reserved words or sequences, I think that
> identifiers like that should be allowed in semantic actions without Bison
> reporting any warnings.
The pattern was stupid and caught occurrences of b4_/m4_ anywhere. The point
was to rather to catch \bb4_ and \bm4_. This is what the attached commit does.
Yes, it does mean that if someone uses b4_foo or m4_foo, she'll get a spurious
warning. If that's really a problem, I'll have to introduce a dedicated -W.
But that would lessen the interest of the warning, if most people don't enable
it.
Hum... Actually "escaping" the user's input to avoid the warning would be a
better option. I'll think about it.
Cheers!
commit c95d0dd5f54b98825e4cfe00a807db78a073e376
Author: Akim Demaille <akim.demaille@gmail.com>
Date: Sat Nov 6 19:24:04 2021 +0100
warnings: be less picky about occurrences of m4_/b4_ in the output
Reported by Marko Mäkelä.
<https://lists.gnu.org/r/bug-bison/2021-10/msg00026.html>
* src/scan-skel.l: It is ok to have foob4_ or foom4_.
* tests/skeletons.at (Suspicious sequences): New.
diff --git a/THANKS b/THANKS
index be743a23..14e678c0 100644
--- a/THANKS
+++ b/THANKS
@@ -117,6 +117,7 @@ Marc Autret autret_m@epita.fr
Marc Mendiola mmendiol@usc.edu
Marc Schönefeld marc.schoenefeld@gmx.org
Mark Boyall wolfeinstein@gmail.com
+Marko Mäkelä marko.makela@iki.fi
Martin Blais blais@furius.ca
Martin Jacobs martin.jacobs@arcor.de
Martin Mokrejs mmokrejs@natur.cuni.cz
diff --git a/src/scan-skel.l b/src/scan-skel.l
index 60232a2e..5a93ce03 100644
--- a/src/scan-skel.l
+++ b/src/scan-skel.l
@@ -54,7 +54,9 @@ static void output_mapped_file (char const *name);
%}
/* Identifiers of our M4 macros. */
-macro [bm]4_[a-zA-Z_0-9]*
+macro [bm]4_[a-zA-Z_0-9]*
+/* Safe sequence of word-constituent characters. */
+identifier [A-Za-z_0-9]+
%x SC_AT_DIRECTIVE_ARGS
%x SC_AT_DIRECTIVE_SKIP_WS
@@ -90,7 +92,7 @@ macro [bm]4_[a-zA-Z_0-9]*
/* This pattern must not match more than the previous @ patterns. */
@[^@{}''(\n]* fail_for_invalid_at (yytext);
\n out_lineno++; ECHO;
-[^bm@\n]+ ECHO;
+[^a-z@\n]+ ECHO;
/* If there are still identifiers that look like macros, such as
b4_synbol, this probably an error, say a typo in M4, or
@@ -104,6 +106,7 @@ macro [bm]4_[a-zA-Z_0-9]*
"suspicious sequence in the output: %s", yytext);
ECHO;
}
+{identifier} ECHO;
. ECHO;
<INITIAL><<EOF>> {
diff --git a/tests/skeletons.at b/tests/skeletons.at
index 0ed11027..30f25a61 100644
--- a/tests/skeletons.at
+++ b/tests/skeletons.at
@@ -324,3 +324,44 @@ AT_SETUP([[Fatal errors but M4 continues producing
output]])
]])
AT_CLEANUP
+
+
+## ---------------------- ##
+## Suspicious sequences. ##
+## ---------------------- ##
+
+AT_SETUP([[Suspicious sequences]])
+
+AT_DATA([[skel.c]],
+[[m4@&t@_include(b4_skeletonsdir/[c.m4])
+m4@&t@_divert_push(0)d@&t@nl
+@output(b4_parser_file_name@)d@&t@nl
+]b4_user_pre_prologue[
+]b4_user_post_prologue[
+b4_unevaluated
+m4@&t@_unevaluated
+]b4_epilogue[
+
+m4@&t@_divert_pop(0)
+]])
+
+AT_DATA([[input1.y]],
+[[%skeleton "./skel.c"
+%{
+ myb4_unevaluated
+ mym4_unevaluated
+%}
+%%
+start: ;
+%%
+myb4_unevaluated
+mym4_unevaluated
+]])
+
+AT_BISON_CHECK([[input1.y]], [], [],
+[[input1.tab.c:10: warning: suspicious sequence in the output: b4_unevaluated
[-Wother]
+input1.tab.c:11: warning: suspicious sequence in the output:
m4@&t@_unevaluated [-Wother]
+]])
+
+
+AT_CLEANUP
- Re: Bogus Bison 3.8.2 warning: suspicious sequence in the output,
Akim Demaille <=