Re: using C++ STL containers in GCC/gfortran source code

[Pedro Alves <pedro at palves dot net>]

On 12/16/2016 06:04 PM, Jakub Jelinek wrote:
> On Fri, Dec 16, 2016 at 06:55:12PM +0100, Janus Weil wrote:
>> To get to more specific questions ...
>>
>>> Basically the only STL construct used in the Fortran FE right now
>>> seems to be std::swap, and a single instance of std::map in
>>> trans-common.c.
>>
>> I see that fortran/trans-common.c has:
>>
>> #define INCLUDE_MAP
>>
>> and apparently there is also a INCLUDE_STRING macro. I guess if I want
>> to use std::string I don't #include <string>, but #define
>> INCLUDE_STRING, right? Why are those macros needed, exactly?
> 
> They are needed because system.h poisons lots of things, including malloc
> etc.  So including system headers after system.h is problematic.

IMO, GCC's poison (or a variant) should ignore system headers.  There's
nothing one can do with those.  It's _uses_ in one's code that generally
one wants to prevent with the poisoning.

> 
> That said, using std::string for what you talk in the PR would make it
> impossible to translate it, if you build a sentence as:
>   ss << "Argument " << something () << " and '" << something_else () << "'";
> then our framework can't deal with that, translating portions of a sentence
> is not going to be useful for many languages.
> Using *printf or similar formatting strings allows the translator to see
> the whole sentence with arguments, and e.g. when needed can swap
> some arguments using %4$s syntax etc.

The problem is not std::string here, but the stream operators.
And I agree.

GDB has a string_printf function that prints into a std::string, for
example.  Like:

  std::string hello = string_printf ("%s", "hello world");

That's a function that many C++ projects reinvent.