Re: I want to use the g++ template in the "C" gcc software

On 2024-12-12, aotto1968 <aotto1968@t-online.de> wrote:

Hi,
>
I create a C software and there is a requirement to use the g++
template *in* the gcc.
I do *not* want to use all the g++ "boilerplate" like special syntax, classes etc
I just want to use the template.

 It sounds like you want to work in a subset of C++ which includes the
entire C-like subset, plus template functions.
 (Note that the class keyword in C++ is almost a synonym of struct.
In a dialect of C that has C++ templates, you should be able to justify
allowing yourself to use template structs, not only template functions.)
 

1. Is there a g++ switch to disable all the g++ features except of C source and template feature ?

 g++ has few, if any, diagnostic options for excluding entire C++
features. You can turn off exception handling and RTTI.
 It might also make sense to select an old dialect of C++, perhaps like
this:
    g++ -std=c++98 ...
 (Unless you want to use newer features of C that appeared since C++98
and were added to C++.)
 Obviously, since C++98 had classes, this will not turn off classes.
 I myself maintain some code which is written in C++ that compiles as C
(or vice versa). But because you want to use templates, compiling as C
is out of the question.
 When you stick to a strictly C compatible subset of C++ (no templates),
then ensuring you are not using special C++ features is very simple:
you regularly build the code with a C compiler!
 Sometimes in my programming I have macros which are implemented
separately for C and C++. For instance for casting:
 #ifdef __cplusplus
#define strip_qual(TYPE, EXPR) (const_cast<TYPE>(EXPR))
#define convert(TYPE, EXPR) (static_cast<TYPE>(EXPR))
#define coerce(TYPE, EXPR) (reinterpret_cast<TYPE>(EXPR))
#else
#define strip_qual(TYPE, EXPR) ((TYPE) (EXPR))
#define convert(TYPE, EXPR) ((TYPE) (EXPR))
#define coerce(TYPE, EXPR) ((TYPE) (EXPR))
#endif
 For instance:
     const char *s0 = "abc";
    char *s1 = strip_qual(char *, s0);
 In C, the strip_qual macro generates a C cast: (char *)(s0).
When compiled as C++, it becomes const_cast<char *>(s0).
 Modern C has something called generic selection, which can do some
template-like things. *IF* your intended use of templates were simple
enough, it *might* be possible to wrap it behind some macros that
expand to C++ templates or to C generic selection.
 Just an idea.
 

3. is there an external software to add the c++-template feature into
an existing C software ?

 The first C++ compilers were developed by Bjarne Stroupstrup as a front
end called "cfront" which generated C. The source for that are
available, and date back to the nineties. I believe they have template
support. It's been quite a while since I looked at the code, but I seem
to remember template stuff in there. If so, it's probably behind even
C++98; would it do partial specialization and such? Don't know.
 Anyway, using a forked and stripped down version of cfront, it may be
possible to create a "C With Templates" dialect of C. (C++ was
originally called C With Classes).
 Then you wouldn't need g++ at all; cfront would translate the code
to plain C, compiled with gcc.