vtkAssume.h File Reference

#include "vtkCompiler.h"
#include <cassert>

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Macros
#define	VTK_ASSUME(cond)
	VTK_ASSUME instructs the compiler that a certain non-obvious condition will always be true.
#define	VTK_ASSUME_NO_ASSERT(cond)
#define	VTK_ASSUME_IMPL(cond)

Macro Definition Documentation

VTK_ASSUME

#define VTK_ASSUME

(

cond

)

Value:

  do                                                                                               \
  {                                                                                                \
    const bool c = cond;                                                                           \
    assert("Bad assumption in VTK_ASSUME: " #cond&& c);                                            \
    VTK_ASSUME_IMPL(c);                                                                            \
    (void)c;      /* Prevents unused var warnings */                                               \
  } while (false) /* do-while prevents extra semicolon warnings */

VTK_ASSUME instructs the compiler that a certain non-obvious condition will always be true.

Beware that if cond is false at runtime, the results are unpredictable (and likely catastrophic). A runtime assertion is added so that debugging builds may easily catch violations of the condition.

A useful application of this macro is when a vtkGenericDataArray subclass has a known number of components at compile time. Adding, for example, VTK_ASSUME(array->GetNumberOfComponents() == 3); allows the compiler to provide faster access through the GetTypedComponent method, as the fixed data stride in AOS arrays allows advanced optimization of the accesses.

A more detailed description of this class and related tools can be found here.

Definition at line 30 of file vtkAssume.h.

VTK_ASSUME_NO_ASSERT

#define VTK_ASSUME_NO_ASSERT

(

cond

)

Value:

  do                                                                                               \
  {                                                                                                \
    const bool c = cond;                                                                           \
    VTK_ASSUME_IMPL(c);                                                                            \
    (void)c;      /* Prevents unused var warnings */                                               \
  } while (false) /* do-while prevents extra semicolon warnings */

Definition at line 39 of file vtkAssume.h.

VTK_ASSUME_IMPL

#define VTK_ASSUME_IMPL

(

cond

)

Value:

  do                                                                                               \
  {                                                                                                \
  } while (false) /* no-op */

Definition at line 55 of file vtkAssume.h.