* Segher Boessenkool: > On Fri, Oct 18, 2019 at 12:47:49PM +0200, Florian Weimer wrote: >> > #define symbol_set_declare(set) \ >> > extern char const __start_##set[] __symbol_set_attribute; \ >> > extern char const __stop_##set[] __symbol_set_attribute; >> > >> > Due to symbol_set_declare, those symbols expand to two unrelated >> > symbols. Using unrelated symbols for pointer arithmetic again violates the >> > standard. >> >> Ah. So we need more uintptr_t casts here. > > Using reserved names (like those starting with two underscores) is UB > already. And those particular names actually clash with names GNU LD > already creates! Well, those names are created by BFD ld for us as well. But that doesn't mean that GNU C will do anything sensible with them. You do not need C language extensions for that. Some of them an non-controversial, others less so. >> > Thus, the issue that Martin mentioned applies here, too. >> > >> > To get this conforming, the linker would need to export a symbol to the start >> > of the section and the length of the section, IMHO. >> >> Right, but we do not have that today. 8-( > > We have had it since over 25 years: > > Thu Aug 18 15:37:45 1994 Ian Lance Taylor (ian@xxxxxxxxxxxxxxxxxxx) > > Make the ELF linker handle orphaned sections reasonably. Also, > define __start_SECNAME and __stop_SECNAME around sections whose > names can be represented in C, for the benefit of symbol sets in > glibc. > > You just need to have linker scripts that do not sabotage this :-) But it doesn't work on s390x if the section has a size that is not a multiple of 2 because all global symbols must have alignment 2 or more on that architecture (of course __alignof (symbol) may still say 1 because *that* has to reflect C semantics). Thanks, Florian
