BSP Developer's Guide

VxWorks 5.5
BSP Developer’s Guide
the compilers supports the Altivec processor and the built-in DSP functions it
provides. Your code should avoid the use of vector as a variable name.
Statement Labels
The ANSI specification requires labels to be associated with statements. It is not
uncommon to place labels at the end of a code block without any associated
statement at all. With strict ANSI checking this is an error. In the code below the
default label is not connected to a statement. To correct this problem, either remove
the label or add a null statement to give the label a proper point of connection.
switch (xxx)
{
case X: statement;
case Y: statement;
default: /* WRONG – no statement here */
}
Summary of Compiler Macros
For each supported C toolchain, the macros described in this section are defined
when vxWorks.h is included in your compilation.
_WRS_PACK_ALIGN(n)
This macro is used to specify the packing and alignment attributes for a structure.
Packing insures that no padding is inserted and that the minimum field alignment
within the structure is one byte. The user can specify the assumed alignment for
the structure as a whole with the argument x, in bytes. The value x is expected to
be a power of two value (1,2,4,8,…). The size of the structure is then a multiple of
this value. If the overall structure alignment is 1, the compiler assumes that this
structure, and any pointer to this structure, can exist on any possible alignment.
For an architecture that cannot handle misaligned data transfers, the compiler is
forced to generate code to access each byte separately and then to assemble the
data into larger word and longword units.
The macro is placed after the closing brace of the structure field description and
before any variable item declarations, or typedef name declarations.
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