Red Hat Bugzilla – Bug 103873
Info documents non-existent math functions
Last modified: 2007-03-27 00:09:36 EDT
Description of problem: Functions log2, exp2, exp10 are documented in info, but not in manpages. The functions do not exist. Version-Release number of selected component (if applicable): 2.3.2-27.9 How reproducible: Always Steps to Reproduce: 1. pinfo libc, go to Mathematics 2. Find listed functions documented 3. Go to manpage, use in program, futz around in the math.h header, ... Actual results: Listed functions aren't there (no manpage, not in the math.h header or library either) Expected results: Just existing functions documented? ;-) Additional info: I believe all those are non-essential GNU extensions (or where at some point in time), they could safely just be removed from the documentation.
The functions of exist. exp2/log2 are ISO C99 functions, so one of -std=c99, -std=gnu99, -D_ISOC99_SOURCE or -D_GNU_SOURCE is needed to get their prototypes in math.h (info libc talks about feature macros). exp10 and pow10 are GNU extensions, so -D_GNU_SOURCE is needed to get their prototypes.
Then the fact that extra magic is needed to get them is not documented is certainly a bug, as is the fact that they aren't documented in manpages...
info libc doesn't mention this for any function (nor it mentions which header provides which prototype), it just notes (e.g. for exp10/pow10) that the functions are GNU extensions, which in standard headers implies -D_GNU_SOURCE). Man pages should list things like this, but they are missing (also for lots of other functions). Changing this to enhancement request for man pages (patches appreciated as always).
the info pages will always be the authoritive source and will never be as complete as the info pages unfortunately. it would be nice if either/both drew there docs from a common source, but they don't.