“#pragma”命令中的变量“undeclared”?

我正在编译 Blender 三维建模程序 from source (使用 SCONS ),我遇到了一个在CentOS 5上编译同一个源代码时没有遇到的错误,我认为这与变量定义有关。错误是:

source/blender/blenkernel/intern/implicit.c: In function ‘mul_bfmatrix_lfvector’:
source/blender/blenkernel/intern/implicit.c:592: error: ‘CLOTH_OPENMP_LIMIT’ undeclared (first use in this function)
source/blender/blenkernel/intern/implicit.c:592: error: (Each undeclared identifier is reported only once
source/blender/blenkernel/intern/implicit.c:592: error: for each function it appears in.)
source/blender/blenkernel/intern/implicit.c: In function ‘cloth_calc_force’:
source/blender/blenkernel/intern/implicit.c:1700: error: ‘CLOTH_OPENMP_LIMIT’ undeclared (first use in this function)

文件 implicit.c 是否定义了该变量;以下是文件的前几行:

#include "MEM_guardedalloc.h"

#include "BKE_cloth.h"

#include "DNA_object_force.h"

#include "BKE_effect.h"
#include "BKE_global.h"
#include "BKE_utildefines.h"

#include "BLI_threads.h"

#define CLOTH_OPENMP_LIMIT 25

#ifdef _WIN32
#include <windows.h>
static LARGE_INTEGER _itstart, _itend;
static LARGE_INTEGER ifreq;

引发错误的两行是:

#pragma omp parallel sections private(i) if(vcount > CLOTH_OPENMP_LIMIT)

#pragma omp parallel for private(i) if(numverts > CLOTH_OPENMP_LIMIT)

我猜这个错误是由于编译器以及它在编译中定义变量时的处理方式造成的,而且由于Fedora8有点过时,它可能有一个旧版本的编译器把它搞乱了。有人知道我如何绕过这个显示为“undeclared”的变量吗?