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.

goal:

1. I already use "inline" code to replace "cpp-macro-like" syntax in the header.
2. NOW I *want* to replace a "cpp-macro" which use the *data-type* as an argument with a template.

question.

1. Is there a g++ switch to disable all the g++ features except of C source and template feature ?
2. Is there a gcc switch to add g++-template feature into gcc ?
3. is there an external software to add the c++-template feature into an existing C software ?

thanks.

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On 12/12/2024 09:37, aotto1968 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.

goal:

1. I already use "inline" code to replace "cpp-macro-like" syntax in the header.
2. NOW I *want* to replace a "cpp-macro" which use the *data-type* as an argument with a template.

question.

1. Is there a g++ switch to disable all the g++ features except of C
source and template feature ?
2. Is there a gcc switch to add g++-template feature into gcc ?
3. is there an external software to add the c++-template feature into an existing C software ?

thanks.

It might help if you give an example of what you are trying to achieve -
it doesn't have to be valid code that can be compiled.

gcc has command-line options to disable some features of C and C++, but
not like you are describing. And C++ without classes is not the same as
C anyway. But you might find you can write your code in C++ and simply
not use the features you don't want to use.

If you are trying to make type-generic function-like "things" in C, then
you have to use macros. But you can use modern features of C11 and C23
to make this safer and neater than in older C standards. gcc also
provides extensions that can help, if you are happy writing gcc-specific
code.

You should do your own googling for information, tutorials and examples
here, but these links will give you some starting points:

C11 _Generic selections:
<https://en.cppreference.com/w/c/language/generic>

C23 "typeof" and "auto" type inference: <https://en.cppreference.com/w/c/language/typeof> <https://en.cppreference.com/w/c/language/auto>

gcc extensions:
<https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html> <https://gcc.gnu.org/onlinedocs/gcc/Typeof.html>

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On 12.12.24 11:24, David Brown wrote:

On 12/12/2024 09:37, aotto1968 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.

goal:

1. I already use "inline" code to replace "cpp-macro-like" syntax in the header.
2. NOW I *want* to replace a "cpp-macro" which use the *data-type* as an argument with a template.

question.

1. Is there a g++ switch to disable all the g++ features except of C source and template feature ?
2. Is there a gcc switch to add g++-template feature into gcc ?
3. is there an external software to add the c++-template feature into an existing C software ?

thanks.

It might help if you give an example of what you are trying to achieve - it doesn't have to be valid code that can be compiled.

gcc has command-line options to disable some features of C and C++, but not like you are describing.  And C++ without classes is
not the same as C anyway.  But you might find you can write your code in C++ and simply not use the features you don't want to use.

If you are trying to make type-generic function-like "things" in C, then you have to use macros.  But you can use modern
features of C11 and C23 to make this safer and neater than in older C standards.  gcc also provides extensions that can help, if
you are happy writing gcc-specific code.

You should do your own googling for information, tutorials and examples here, but these links will give you some starting points:

C11 _Generic selections:
<https://en.cppreference.com/w/c/language/generic>

C23 "typeof" and "auto" type inference: <https://en.cppreference.com/w/c/language/typeof> <https://en.cppreference.com/w/c/language/auto>

gcc extensions:
<https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html> <https://gcc.gnu.org/onlinedocs/gcc/Typeof.html>

Thanks for your links but I already know "feature" of gcc etc…

I still want to get better "macro" code use template like c++ has

example: (the 'cls' is a type and the `pBufferInit_T` create a type specific "inline"

this I want to replace with an template.

#define pBufferInit_T(pre, cls) \
mk_inline void \
p##cls##Init ( \
MK_RT_ARGS \
pre##cls##C##R * const loc, \
MK_TYP const type, \
MK_NUM const size \
) { \
pppBufferInit(MK_RT_CALL pre##cls##C##_X2buf(loc),size, \
(MK_NUM)((*type).objsize-sizeof(pre##cls##C##R)), \
offsetof(pre##cls##C##R,ils_data)); \
if (type->objsig != (*pre##cls##C##_X2obj(loc)).signature) { \
(*pre##cls##C##_X2obj(loc)) = MkObjInitFromType(type,true /* isLocal */); \
} \
/* ppBufferInit */ \
/* ppBufferStreamInit */ \
pp##cls##Init(MK_RT_CALL loc); \
/* pBufferReset */ \
/* pBufferStreamReset */ \
p##cls##Reset(loc); \
} \

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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.


--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

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On 12.12.24 20:09, Kaz Kylheku wrote:

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.

thanks, good summary.

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On 2024-12-12, Chris M. Thomasson <chris.m.thomasson.1@gmail.com> wrote:

ot, but some fun with macros:

https://github.com/rofl0r/chaos-pp

When the C preprocessor gets applied to a language with a lighter
syntax without declaations, things really start happening.

https://kylheku.com/cgit/cppawk/about

cppawk ships with an iteration macro that takes multiple clauses that
are taken in parallel or cross-product wise. Moreover, the vocabulary
of loop clauses can be extended by the program, by writing a few simple
macros (per clause).

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

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On 12/12/2024 08:37, aotto1968 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.

goal:

1. I already use "inline" code to replace "cpp-macro-like" syntax in the header.
2. NOW I *want* to replace a "cpp-macro" which use the *data-type* as an argument with a template.

question.

1. Is there a g++ switch to disable all the g++ features except of C
source and template feature ?
2. Is there a gcc switch to add g++-template feature into gcc ?
3. is there an external software to add the c++-template feature into an existing C software ?

thanks.

What is the latest version og GCC/G++ and how to upgrade? On my version
I can't seem to compile Modern C++ snippets. My version is:

g++ (Rev3, Built by MSYS2 project) 14.1.0

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