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diagnostics: modernize bison's syntax errors

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We used to display the unexpected token first:

    $ bison foo.y
    foo.y:1.8-13: error: syntax error, unexpected %token, expecting character literal or identifier or <tag>
        1 | %token %token
          |        ^~~~~~

GCC uses a different format:

    $ gcc-mp-9 foo.c
    foo.c:1:5: error: expected identifier or '(' before ')' token
        1 | int()()()
          |     ^

and so does Clang:

    $ clang-mp-9.0 foo.c
    foo.c:1:5: error: expected identifier or '('
    int()()()
        ^
    1 error generated.

They display the unexpected token last (or not at all).  Also, they
don't waste width with "syntax error".  Let's try that.  It gives, for
the same example as above:

    $ bison foo.y
    foo.y:1.8-13: error: expected character literal or identifier or <tag> before %token
        1 | %token %token
          |        ^~~~~~

* src/complain.h, src/complain.c (syntax_error): New.
* src/parse-gram.y (yyreport_syntax_error): Use it.
This commit is contained in:
Akim Demaille
2020-01-22 23:24:20 +01:00
parent 6fb362c87a
commit fc2191f137
5 changed files with 88 additions and 68 deletions
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53
src/parse-gram.y
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@@ -804,58 +804,17 @@ epilogue.opt:
int
yyreport_syntax_error (const yyparse_context_t *ctx)
{
if (complaint_status < status_complaint)
complaint_status = status_complaint;
enum { YYERROR_VERBOSE_ARGS_MAXIMUM = 5 };
/* Internationalized format string. */
const char *format = YY_NULLPTR;
/* Arguments of format: reported tokens (one for the "unexpected",
one per "expected"). */
int arg[YYERROR_VERBOSE_ARGS_MAXIMUM];
int n = yysyntax_error_arguments (ctx, arg, YYERROR_VERBOSE_ARGS_MAXIMUM);
switch (n)
{
case -2:
return 2;
# define YYCASE_(N, S) \
case N: \
format = S; \
break
default: /* Avoid compiler warnings. */
YYCASE_(0, YY_("syntax error"));
YYCASE_(1, YY_("syntax error, unexpected %s"));
YYCASE_(2, YY_("syntax error, unexpected %s, expecting %s"));
YYCASE_(3, YY_("syntax error, unexpected %s, expecting %s or %s"));
YYCASE_(4, YY_("syntax error, unexpected %s, expecting %s or %s or %s"));
YYCASE_(5, YY_("syntax error, unexpected %s, expecting %s or %s or %s or %s"));
# undef YYCASE_
}
location_print (*yyparse_context_location (ctx), stderr);
fputs (": ", stderr);
begin_use_class ("error", stderr);
fputs ("error:", stderr);
end_use_class ("error", stderr);
fputc (' ', stderr);
{
int i = 0;
while (*format)
if (format[0] == '%' && format[1] == 's' && i < n)
{
const char *style = i == 0 ? "unexpected" : "expected";
begin_use_class (style, stderr);
fputs (yysymbol_name (arg[i]), stderr);
end_use_class (style, stderr);
format += 2;
++i;
}
else
{
fputc (*format, stderr);
++format;
}
}
fputc ('\n', stderr);
location_caret (*yyparse_context_location (ctx), "error", stderr);
if (n == -2)
return 2;
const char *argv[YYERROR_VERBOSE_ARGS_MAXIMUM];
for (int i = 0; i < n; ++i)
argv[i] = yysymbol_name (arg[i]);
syntax_error (*yyparse_context_location (ctx), n, argv);
return 0;
}