Bullet 2.82 and btInfinityMask compiler warning

[Ingar]

I'm in the habit of compiling my C++ project with -Wall -Werror to catch potential problems
as early as possible. Unfortunatly bullet 2.82 generates a warning, forcing me to disable -Werror.

The error message, gcc version is 4.8.2 (Arch Linux):

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/usr/include/bullet/LinearMath/btScalar.h:337:14: warning: 'btInfinityMask' defined but not used [-Wunused-variable]
  static  int btInfinityMask = 0x7F800000;
              ^

It is only a warning, but it is annoying, as it clutters my build log. A workaround to make the message go away would be greatly appreciated.

[c6burns]

http://dbp-consulting.com/tutorials/Sup ... nings.html

[Ingar]

Solved it for now by adding an extra definition to my own header files.

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#if (BT_BULLET_VERSION == 282)
inline int bullet_btInfinityMask()
{
	return btInfinityMask;
}
#endif

In the end, this is just as bad as special #pragma directives or preprocessor flags,
but at least it only suppresses this particular warning.

[Erwin Coumans]

That flag is only used for some SSE/SIMD code, and we don't enable that for your compiler/platform combination, hence it is unused.

We could add that line in btScalar.h (without the version check), would that help you?

inline int bullet_btInfinityMask()
{
return btInfinityMask;
}

[Ingar]

It does solve the issue for me. Note that I didn't actually change the bullet header, but my own header that #includes btScalar.h.
Maybe it's possible to #ifdef the btInfinityMask definition such that it dissapears if the SIMD implementation isn't being used.

[marzoul]

We could add that line in btScalar.h (without the version check), would that help you?

inline int bullet_btInfinityMask()
{
return btInfinityMask;
}

Depending on optimization levels and debug parameters (-g), inline functions may not be kept and compiled, so the warning could remain. Plus it's a definition of an unuseful function, and it lets btInfinityMask instantiated as a variable in each source file the header is included, just because of a cast.

I see two other solutions, IMHO a bit cleaner.

Fist the variable could be declared with the attribute "unused" (GCC and Clang handle this):

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__attribute((__unused__)) static  int btInfinityMask = 0x7F800000;

Or, don't try to define BT_INFINITY, instead define btInfinityMask as macro and the following function:

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#define btInfinityMask 0x7F800000
static inline int btIsInfinity(float f) {
    return (*(int*)&f) == btInfinityMask;
}