OpenBLAS/common_stackalloc.h

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#define STACK_ALLOC_PROTECT
#ifdef STACK_ALLOC_PROTECT
// Try to detect stack smashing
#include <assert.h>
#define STACK_ALLOC_PROTECT_SET volatile int stack_check = 0x7fc01234;
#define STACK_ALLOC_PROTECT_CHECK assert(stack_check == 0x7fc01234);
#else
#define STACK_ALLOC_PROTECT_SET
#define STACK_ALLOC_PROTECT_CHECK
#endif

#if defined(MAX_STACK_ALLOC) && MAX_STACK_ALLOC > 0

/*
 * Allocate a buffer on the stack if the size is smaller than MAX_STACK_ALLOC.
 * Stack allocation is much faster than blas_memory_alloc or malloc, particularly
 * when OpenBLAS is used from a multi-threaded application.
 * SIZE must be carefully chosen to be:
 * - as small as possible to maximize the number of stack allocation
 * - large enough to support all architectures and kernel
 * Choosing a SIZE too small will lead to a stack smashing.
 */
#define STACK_ALLOC(SIZE, TYPE, BUFFER)                                        \
  /* make it volatile because some function (ex: dgemv_n.S) */                 \
  /* do not restore all register */                                            \
  volatile int stack_alloc_size = SIZE;                                        \
  if (stack_alloc_size > MAX_STACK_ALLOC / sizeof(TYPE)) stack_alloc_size = 0; \
  STACK_ALLOC_PROTECT_SET                                                      \
  /* Avoid declaring an array of length 0 */                                   \
  TYPE stack_buffer[stack_alloc_size ? stack_alloc_size : 1]                   \
      __attribute__((aligned(0x20)));                                          \
  BUFFER = stack_alloc_size ? stack_buffer : (TYPE *)blas_memory_alloc(1);
#else
  //Original OpenBLAS/GotoBLAS codes.
  #define STACK_ALLOC(SIZE, TYPE, BUFFER) BUFFER = (TYPE *)blas_memory_alloc(1)
#endif


#if defined(MAX_STACK_ALLOC) && MAX_STACK_ALLOC > 0
#define STACK_FREE(BUFFER)    \
  STACK_ALLOC_PROTECT_CHECK   \
  if(!stack_alloc_size)       \
    blas_memory_free(BUFFER);
#else
#define STACK_FREE(BUFFER) blas_memory_free(BUFFER)
#endif