What's that preprocessor do
#ifdef __cplusplus
extern "C" {
#endif
..
..
..
#ifdef __cplusplus
}
#endif
and how you say extern "C" , i mean how u extern constant!!
5  2928 
"Medvedev" <3D********@gma il.comwrote in message
news:7f******** *************** ***********@t54 g2000hsg.google groups.com...
What's that preprocessor do
#ifdef __cplusplus
extern "C" {
#endif
.
.
.
#ifdef __cplusplus
}
#endif
and how you say extern "C" , i mean how u extern constant!!
extern "C"
{
}
... causes any functions inside the braces to have
"C linkage", so that they can be called from C
functions. There's nothing about 'constant' here.
The #ifdef will cause 'extern C' to be applied only
if translating C++ code.
-Mike
On Jul 6, 2:12 pm, "Mike Wahler" <mkwah...@mkwah ler.netwrote:
"Medvedev" <3D.v.Wo...@gma il.comwrote in message
news:7f******** *************** ***********@t54 g2000hsg.google groups.com...
What's that preprocessor do
#ifdef __cplusplus
extern "C" {
#endif
.
.
.
#ifdef __cplusplus
}
#endif
and how you say extern "C" , i mean how u extern constant!!
extern "C"
{
}
.. causes any functions inside the braces to have
"C linkage", so that they can be called from C
functions. There's nothing about 'constant' here.
sorry , but what differ C++ functions from C ones
"Medvedev" <3D********@gma il.comwrote in message
news:ce******** *************** ***********@e53 g2000hsa.google groups.com...
On Jul 6, 2:12 pm, "Mike Wahler" <mkwah...@mkwah ler.netwrote:
>"Medvedev" <3D.v.Wo...@gma il.comwrote in message
news:7f******* *************** ************@t5 4g2000hsg.googl egroups.com...
What's that preprocessor do
#ifdef __cplusplus
extern "C" {
#endif
.
.
.
#ifdef __cplusplus
}
#endif
and how you say extern "C" , i mean how u extern constant!!
extern "C"
{
}
.. causes any functions inside the braces to have
"C linkage", so that they can be called from C
functions. There's nothing about 'constant' here.
sorry , but what differ C++ functions from C ones
C++ functions have overloading. C functions do not. This means there is
only one definition for a C function, there can be more than one for a C++
function. Compilers typcially handle this by "mangling". This will change
the name of the C++ function in the object file so the linker can
differentiate between calling parameters.
stating:
extern "C" {
tells the compiler not to mangle the function names, there will only be one
declaration for each function, so then when it is linked it has C linkage,
the function name would be the same as if it was a C function, and C
programs/objects can call the function as they can now link to them.
"Medvedev" <3D********@gma il.comwrote in message
news:ce******** *************** ***********@e53 g2000hsa.google groups.com...
On Jul 6, 2:12 pm, "Mike Wahler" <mkwah...@mkwah ler.netwrote:
>"Medvedev" <3D.v.Wo...@gma il.comwrote in message
news:7f******* *************** ************@t5 4g2000hsg.googl egroups.com...
What's that preprocessor do
#ifdef __cplusplus
extern "C" {
#endif
.
.
.
#ifdef __cplusplus
}
#endif
and how you say extern "C" , i mean how u extern constant!!
extern "C"
{
}
.. causes any functions inside the braces to have
"C linkage", so that they can be called from C
functions. There's nothing about 'constant' here.
sorry , but what differ C++ functions from C ones
Think about overloading. You can have more than a
single function with the same name (the number and/or
types of arguments would differ.
int foo(void);
int foo(int);
int foo(int,int);
C++ needs to distinguish these functions from one another.
There's no specific method required by the standard, but
typically the compiler will 'mangle' the names (change and/or
add characters) so that they become unique.
"extern C" prevents this 'mangling', so that the function
can be linked with C (using its 'real' name).
Anyway, I should have already cited this link from the C++ FAQ: http://www.parashift.com/c++-faq-lit...c-and-cpp.html
This explains it better than I.
-Mike
On Jul 7, 12:18 am, Medvedev <3D.v.Wo...@gma il.comwrote:
On Jul 6, 2:12 pm, "Mike Wahler" <mkwah...@mkwah ler.netwrote:
"Medvedev" <3D.v.Wo...@gma il.comwrote in message
news:7f******** *************** ***********@t54 g2000hsg.google groups.com....
What's that preprocessor do
#ifdef __cplusplus
extern "C" {
#endif
.
.
.
#ifdef __cplusplus
}
#endif
and how you say extern "C" , i mean how u extern constant!!
extern "C"
{
}
.. causes any functions inside the braces to have
"C linkage", so that they can be called from C
functions. There's nothing about 'constant' here.
sorry , but what differ C++ functions from C ones
Whatever the implementation wants. There's no fundamental
reason for two different languages to use the same calling
conventions. One typical difference might be that in C++, the
call stack is cleaned up in the called function (since it
involves calling destructors, etc.), where as in C, it is
cleaned up in the callee (since historically, C didn't have
prototypes, and allowed calling a function with extra arguments,
which were ignored). Also, C++ has overloading, which means
that some sort of information concerning the type and number of
arguments must be maintained in the object file. And because C
allowed extra arguments, a C compiler will not want to do this.
--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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