HP aC++/HP C Programmer's Guide (B3901-90036; A.06.26; September 2011)

num_threads
num_threads(interger-expression)
The num_threads clause allows a user to request a specific number of threads for a
parallel construct. If the num_threads clause is present, then the value of the integer
expression is the number of threads requested.
Attributes
__attribute__ is a language feature that allows you to add attributes to functions (or
with the aligned attribute, to variables or structure fields). The capabilities are similar
to those of #pragma. It is more integrated into the language syntax than pragmas and
its placement in the source code depends on the construct to which the attribute is being
applied.
The attributes supported are:
• aligned
• malloc
• non_exposing
• noreturn
• format
• visibility
• warn_unused_result
attribute aligned
__attribute__ (aligned (alignment))
The aligned attribute specifies the minimum alignment for a variable or structure field,
measured in bytes. For example, the following declaration causes the compiler to allocate
the global variable x on a 16-byte boundary:
int x __attribute__ ((aligned (16))) = 0;
You can also specify the alignment of structure fields. For example, the following causes
the compiler to allocate the field member "x" to be aligned on a 128-byte boundary:
struct foo { int x[2] __attribute__ ((aligned (128)));}
The maximum alignment that can be specified is 128. This feature is for compatibility
with gcc.
attribute malloc
__attribute__ ((malloc))
The malloc attribute is used to improve optimization by telling the compiler that:
142 Pragma Directives and Attributes