Re: Porting C to C++
Paul wrote:
Hi,
I am porting a piece of code from C to C++. The C code has a macro
like this:
#define MALLOC(p, b, s) {if ((b) > 0) { \
p= malloc(b); if (!(p)) { \
fprintf(stderr, "memory allocation error:
%s\n", s); \
exit(0);}} else p= NULL;}
the g++ compiler complains about "invalid conversion from void* to"
xxx* because of the lack of a cast in front of p.
Is there a way to fix this macro so that it can work in C++?
Yes, write
p = new xxx;
There is rarely need for malloc in C++ code, and if so, it is usually
for low-level memory handling or allocation of raw buffers (then, p is
usually something like a "char *") for legacy interfaces.
Otherwise, I would suggest to cast outside of MALLOC, an make it an
inline function instead:
inline void *MALLOC(size_t b,const char *s)
{
....
}
and then use it as such: p = (xxx *)MALLOC(...) *if* xxx is a POD. Note
that casting to the proper type is required in C++ for a "raw" malloc as
well.
C++0x will provide features to derive the type of an object, somewhat
resolving the situation, but nevertheless, the proper way is to use the
new expression here.
So long,
Thomas
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