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M4 problem for yacc.c parser.

From: A.Steenveld
Subject: M4 problem for yacc.c parser.
Date: Tue, 22 Jul 2008 11:24:58 +0200

When compiling the bison output based on skeleton yacc.c Microsoft Visual
Studio C/C++ complains "error C2449: found '{' at file scope (missing function
header?)" at file yy.yacc.c at line 885.

Removing a semicolon at line 882 corrects the problem.

The bit of code concerning this complaint runs as follows:
*** lines 864-886 from yy.yacc.c
| yyparse.  |

# if defined (__STDC__) || defined (__cplusplus)
int yyparse (void *YYPARSE_PARAM)
# else
int yyparse (YYPARSE_PARAM)
# endif
#else /* ! YYPARSE_PARAM */
#if defined (__STDC__) || defined (__cplusplus)
yyparse (void)
yyparse ()
    ;             /* <<<--- line 882 */
{                 /* <<<--- line 885 */
*** end lines 864-886 from yy.yacc.c

The direct problem is caused 3 lines above, line 882, by the single semicolon.

This semicolon is inserted by the M4 generator used on the skeleton file
yacc.c, in particular the macro's b4_c_knr_formal_decls, wich reads like

*** lines 268-279 from ...\GnuWin32\share\bison\c.m4
# b4_c_knr_formal_decls([DECL1, NAME1], ...)
# ------------------------------------------
# Output the K&R argument declarations.

[    $1;])

*** end lines 268-279 from ...\GnuWin32\share\bison\c.m4

These two macro's genereate the lines 880-882 in yy.yacc.c but when called
with an empty argument list it still closes the definition with a semicolon
changing the definition into a declaration and forcing the definition code
block to stand on its own.

I can reason out what is happening but I don't know M4 well enough. Who has
any suggestions to correct the M4 code?

Kind regards,

Andre Steenveld.

Het UMC St Radboud staat geregistreerd bij de Kamer van Koophandel in het 
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The Radboud University Nijmegen Medical Centre is listed in the Commercial 
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