Using Portable Bit Masks

Use scalable masks with scalable typedefs. Scalable types, such as int and long, may be different sizes on different platforms. For example, use the portable bit mask construct:

Solution 1:

#include <inttypes.h>
#ifdef __LP64__
   int64_t node_id=0xfffffffffffffffc;
#else
   int32_t node_id=0xfffffffc;

or:

Solution 2:

#include <inttypes.h>
intmax_t node_id = ~0x3;

instead of the non-portable construct:

long node_id =  0xfffffffc;

When compiled on an HP-UX 32-bit platform, the first 2 constructs above result in the intended value:

1111 1111 1111 1111 1111 1111 1111 1100

However, when compiled on an HP-UX 64-bit platform, the first and second construct produce the correct binary value:

1111 1111 1111 1111 1111 1111 1111 1111
1111 1111 1111 1111 1111 1111 1111 1100

while the third construct generates an incorrect bit mask value:

0000 0000 0000 0000 0000 0000 0000 0000
1111 1111 1111 1111 1111 1111 1111 1100

Use fixed size masks with fixed size type definitions. For example, if you want a 32-bit mask, use the portable construct:

#include <inttypes.h>
int32_t intmask = INT32_MAX;

instead of:

long intmask = 0x7fffffff;

Using Portable Bit Masks

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