llvm-project/libc/utils
Roland McGrath e7228062b2 [libc] Use #undef isascii in specific header
Standard C allows all standard headers to declare macros for all
their functions.  So after possibly including any standard header
like <ctype.h>, it's perfectly normal for any and all of the
functions it declares to be defined as macros.  Standard C requires
explicit `#undef` before using that identifier in a way that is not
compatible with function-like macro definitions.

The C standard's rules for this are extended to POSIX as well for
the interfaces it defines, and it's the expected norm for
nonstandard extensions declared by standard C library headers too.

So far the only place this has come up for llvm-libc's code is with
the isascii function in Fuchsia's libc.  But other cases can arise
for any standard (or common extension) function names that source
code in llvm-libc is using in nonstandard ways, i.e. as C++
identifiers.

The only correct and robust way to handle the possible inclusion of
standard C library headers when building llvm-libc source code is to
use `#undef` explicitly for each identifier before using it.  The
easy and obvious place to do that is in the per-function header.
This requires that all code, such as test code, that might include
any standard C library headers, e.g. via utils/UnitTest/Test.h, make
sure to include those *first* before the per-function header.

This change does that for isascii and its test.  But it should be
done uniformly for all the code and documented as a consistent
convention so new implementation files are sure to get this right.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D94642
2021-01-14 13:25:05 -08:00
..
CPP [libc][obvious] Remove the unused file utils/CPP/StringRef.h. 2020-08-12 12:19:11 -07:00
FPUtil [libc] Add implementation of fmaf. 2021-01-06 17:14:20 -05:00
HdrGen [libc] Use entrypoints.txt as the single source of list of functions for a platform. 2020-10-15 20:46:13 +00:00
LibcTableGenUtil [libc] Add missing TableGen dependency 2020-09-15 14:26:04 +00:00
MPFRWrapper [libc] Add implementation of fmaf. 2021-01-06 17:14:20 -05:00
UnitTest [libc] Use #undef isascii in specific header 2021-01-14 13:25:05 -08:00
buildbot [libc] Add python3 to libc buildbot depedencies. 2020-12-17 08:59:13 -08:00
testutils [libc] Use a wrapper for rand instead of calling std::rand in fma tests. 2021-01-06 15:07:44 -08:00
tools [libc] Refactor WrapperGen to make the flow cleaner. 2020-12-17 08:56:45 -08:00
CMakeLists.txt [libc] Add a tool called WrapperGen. 2020-07-30 16:07:26 -07:00