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C23 makes various standard library functions, that return a pointer into an input array, into macros that return a pointer to const when the relevant argument passed to the macro is a pointer to const. (The requirement is for macros, with the existing function types applying when macro expansion is suppressed. When a null pointer constant is passed, such as integer 0, that's the same as a pointer to non-const.) Implement this feature. This only applies to C, not C++, since such macros are not an appropriate way of doing this for C++ and all the affected functions other than bsearch have overloads to implement an equivalent feature for C++ anyway. Nothing is done to apply such a change to any non-C23 functions with the same property of returning a pointer into an input array. The feature is also disabled when _LIBC is defined, since there are various places in glibc that either redefine these identifiers as macros, or define the functions themselves, and would need changing to work in the presence of these macro definitions. A natural question is whether we should in fact change those places and not disable the macro definitions for _LIBC. If so, we'd need a solution for the places in glibc that define the macro *before* including the relevant header (in order in effect to disable the header declaration of the function by renaming that declaration). One testcase has #undef added to avoid conflicting with this feature and another has const added; -Wno-discarded-qualifiers is added for building zic (but could be removed once there's a new upstream tzcode release that's const-safe with this C23 change and glibc has updated to code from that new release). Probably other places in glibc proper would need const added if we remove the _LIBC conditionals. Another question would be whether some GCC extension should be added to support this feature better with macros that only expand each argument once (as well as reducing duplication of diagnostics for bad usages such as non-pointer and pointer-to-volatile-qualfied arguments). Tested for x86_64.
The files zic.c zdump.c tzfile.h private.h tzselect.ksh version come from the tzcode package by Arthur David Olson et.al. The 'version' file specifies which tzcode version was used. The files africa antarctica asia australasia europe northamerica southamerica pacificnew etcetera factory backward systemv solar87 solar88 solar89 iso3166.tab zone.tab leapseconds yearistype come from the tzdata package by Arthur David Olson et.al. except that its 'yearistype.sh' file is renamed to 'yearistype'. These tzdata files were taken from tzdata 2009i and have not been updated since, as they do not affect glibc installation and are present only for regression testing. Please also see: https://sourceware.org/glibc/wiki/SharedSourceFiles These packages may be found at https://ftp.iana.org/tz/releases/. Commentary should be addressed to tz@iana.org. The subdirectory testdata contains manually edited data files for regression testing purposes.