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Re: syntax_error constructor is declared inline

From: Hans Åberg
Subject: Re: syntax_error constructor is declared inline
Date: Wed, 14 Mar 2018 15:20:19 +0100

> On 14 Mar 2018, at 04:03, Frank Heckenbach <address@hidden> wrote:
> Hans Åberg wrote:
>>> On 13 Mar 2018, at 23:23, Frank Heckenbach <address@hidden> wrote:
>>>> Bison 3.0.4 marks the constructor for the syntax_error class as 'inline'
>>>> when generating a C++ scanner, which results in undefined references when
>>>> the exception is thrown from a separate scanner file. Since this is the
>>>> stated purpose of the syntax_error class (see
>>>> http://lists.gnu.org/archive/html/help-bison/2013-07/msg00010.html), this
>>>> appears to be a bug.
>>> Anyway, do you use the "--defines" option or "%defines" setting to
>>> generate a header that you include in your other source files? If
>>> so, AFAICS, the inline constructor is generated in the same header,
>>> so it should be available in your other source file, too.
>> It ends up in the .cc file even with %defines, it seems. But it
>> should properly be in the header file, and probably the other
>> inlines too.
> I checked it and found that it's only put in the header if
>  %define api.token.constructor
> is set. But that can only be set if
>  %define api.value.type
> is also set. So this indeed seems to be wrong for non-variant users.
> Instead of removing "inline" as suggested in the other bug report
> (which would then break with api.token.constructor), the following
> patch will always put the definition in the header.

It is sort of strange in C++ to not have a header, and having inlines not in 
those. In C, there is a style of include the lexer .c file into the parser .c 
file; perhaps the C++ parser intends to preserve that possibility.

> I will apply this patch in my C++17 version, but since I'm not a
> Bison maintainer, I can't promise it will go in the C++98 parser, or
> in the official Bison sources at all. For now, you can apply the
> patch manually (your installation directory may vary).

Perhaps if there is active development of Bison in the future, these things 
might be integrated.

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