On Mon, 4 Sep 2017, Richard Biener wrote: > always have a consistend "character" size and how the individual > "characters" are encoded. The patch assumes that the array element > type of the STRING_CST can be used to get access to individual > characters by means of the element type size and those elements > are stored in host byteorder. Which means the patch simply handles
It's actually target byte order, i.e. the STRING_CST stores the same sequence of target bytes as would appear on the target system (modulo certain strings such as in asm statements and attributes, for which translation to the execution character set is disabled because those strings are only processed in the compiler on the host, not on the target - but you should never encounter such strings in the optimizers etc.). This is documented in generic.texi (complete with a warning about how it's not well-defined what the encoding is if target bytes are not the same as host bytes). I suspect that, generically in the compiler, the use of C++ might make it easier than it would have been some time ago to build some abstractions around target strings that work for all of narrow strings, wide strings, char16_t strings etc. (for extracting individual elements - or individual characters which might be multibyte characters in the narrow string case, etc.) - as would be useful for e.g. wide string format checking and more generally for making e.g. optimizations for narrow strings also work for wide strings. (Such abstractions wouldn't solve the question of what the format is if host and target bytes differ, but their use would reduce the number of places needing changing to establish a definition of the format in that case if someone were to do a port to a system with bytes bigger than 8 bits.) However, as I understand the place you're patching, it doesn't have any use for such an abstraction; it just needs to copy a sequence of bytes from one place to another. (And even with host bytes different from target bytes, clearly it would make sense to define the internal interfaces to make the encodings consistent so this function still only needs to copy bytes from one place to another and still doesn't need such abstractions.) -- Joseph S. Myers jos...@codesourcery.com
