On Wed, 12 Jun 2002, Miguel Camargo wrote: > I am trying to modify the APR library just to add some specific features > in it and use it in Apache.
What kinds of things, just out of curiosity? > But i have some doubts about the meaning and the differences among the > macro definitions of: The first thing to note is that all of these are always defined -- you check whether their value is 0 or 1 -- as opposed to the HAVE_FOO macros that autoconf provides, which are either defined or undefined. That means the test you should use on all of them is #if and not #ifdef. > APR_HAVE_... These are ones that come straight out of what autoconf provides us, except we've namespace-protected them (and done the 0/1 instead of undef/def thing I mentioned above). So basically this means the system provides some item (typically a header file, a given function, a structure, etc); so APR_HAVE_STDIO_H tells you whether or not stdio.h exists. APR_HAVE_MEMMOVE tells you whether or not the memmove() function is provided by the system, etc. > APR_USE_... These are used where multiple choices are provided by the OS; they tell APR which one to use by default. For example, there might be multiple methods of getting a shared memory segment; one of the APR_USE_SHMEM_* macros will be 1 to tell APR which one to prefer. > APR_HAS_... These are "feature" macros; they tell us that APR has support for some broad feature available (where "broad feature" doesn't map to a single function call or header but rather a whole group of them). For example, APR_HAS_MMAP tells us whether APR's MMAP support is available. APR_HAS_THREADS tells us whether APR was built in multi-threaded mode. And so on. There are a *few* cases where we use HAVE where we should be using HAS, and those ought to be cleaned up. But we're mostly consistent. :) Hope this helps. --Cliff
