[ODE] Re: ALLOCA

[Olivier Michel]

Hi,

I tryed to implement the clever C++ ALLOCA macro to save us from the 
FREEA macro, but I cannot get it work:

#ifdef dDYNAMIC_MEMORY_ALLOCATION

class StackMemory {
public:
  StackMemory( int size ) {
    ptr_ = malloc( size );
  }
  ~StackMemory() {
    free( ptr_ );
  }
  void * ptr_;
};

#define ALLOCA(t,v,s) \
  StackMemory alloca_ ## __LINE__( s ); v = (t*)alloca_ ## __LINE__ .ptr_

#else
#define ALLOCA(t,v,s) v=(t*)dALLOCA16(s)
#endif
[...]
  dReal *AA,*dd,*bb;
  ALLOCA (dReal,AA,n*nskip*sizeof(dReal));
  ALLOCA (dReal,dd,n*sizeof(dReal));
[...]

Here is what I get with gcc 2.96:

gcc -c -Wall -fno-rtti -fno-exceptions -Wall -fomit-frame-pointer 
-ffast-math -Iinclude   -DdNODEBUG -DdDYNAMIC_MEMORY_ALLOCATION -O2 -o 
ode/src/lcp.o ode/src/lcp.cpp
ode/src/lcp.cpp: In function `void dSolveLCPBasic (int, dReal *, dReal
*, dReal *, dReal *, int, dReal *, dReal *)':
ode/src/lcp.cpp:1024: redeclaration of `StackMemory alloca___LINE__'
ode/src/lcp.cpp:1023: `StackMemory alloca___LINE__' previously declared
here

Apparently it is unable to expand the __LINE__ inside a macro... Any hint ?

-Olivier

Jon Watte wrote:

>Regarding ALLOCA, you might not need a FREEA() macro, if you structure the
>macro something like so:
>
>class StackMemory {
>public:
>  StackMemory( int size ) {
>    ptr_ = malloc( size );
>  }
>  ~StackMemory() {
>    free( ptr_ );
>  }
>  void * ptr_;
>};
>
>#define ALLOCA(v,s) \
>  StackMemory alloca_ ## __LINE__( s ); v = alloca_ ## __LINE__ .ptr_
>
>
>Note that this macro needs to take the assigned-to variable as well as the
>size, rather than just the size.
>
>Cheers,
>
>			/ h+
>  
>