Shared library performance improvements

Beginning with HP-UX 11.0, users were not allowed to mix shared and archive libraries. This resulted in a slight increase in function overhead, particularly when routine system function calls were required. The libcres.a archive library has been added to the HP C runtime compiler to reduce this overhead.

Libcres.a is a small archive library that contains standard C routines such as string, memory, and other key functions (described in Table 1-3 “libcres.a symbols” below). The intent of this library is to provide performance-critical applications with the benefit of static linkage to commonly used libc functions. Libcres.a is built using a high level of optimization (+O3) with the HP C optimizing compiler.




	NOTE: There is no functionality impact on applications that use libcres.a.

Libcres.a contains only "leaf functions", i.e., functions that do not call any other functions. Any performance improvement is highly dependent on the application's use of these included functions.

The following symbols are contained in libcres.a:

Table 1-3 libcres.a symbols

libc symbols in libcres.a	Description
`abs()`	return integer absolute value
`bsearch()`	binary search a sorted table
`div()`	integer division and remainder
`ffs()`	find first set bit (BSD)
`insque()`	insert an element in a queue
`labs()`	return long integer absolute value
`ldiv()`	long integer division and remainder
`memchr()`	find first occurrence of byte in memory region
`memcmp()`	compare contents of two memory regions
`memcpy()`	copy memory region to a non-overlapping region
`memmove()`	copy memory region to a possibly overlapping region
`memset()`	fill a memory region with a specified byte
`qsort()`	execute quicker sort
`strcat()`	append string number 2 to string number 1
`strchr()`	get pointer to character in string
`strcmp()`	compare two strings
`strcpy()`	copy string number 2 to string number 1
`strcspn()`	find length of matching substrings
`strlen()`	determine length of string
`strncat()`	append string number 2 to string number 1 (up to a given maximum length)
`strncmp()`	compare two strings (up to a given maximum length)
`strncpy()`	copy string number 2 to string number 1 (up to a given maximum length)
`strrchr()`	get pointer to character in string
`strspn()`	find length of matching substring
`strstr()`	finds a substring in a string
`swab()`	swap bytes

How to use libcres.a

In order to make use of libcres.a, existing makefiles must be modified to include it when linking. Existing applications must also be re-linked in order to make use of libcres.a. The modules of this library are compiled with the HP-UX C compiler using the +O3 optimization flag.

The functions in this library can not be overridden with a user-defined function of the same name, as is the case today with other libc function names.




	CAUTION: If you use `libcres.a`, your other libraries must not contain functions of the same name. Otherwise, unexpected results may occur.

Shared library performance improvements

Technical documentation

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How to use libcres.a