2011/3/8 Eli Zaretskii <e...@gnu.org>: >> Date: Tue, 8 Mar 2011 12:25:37 +0100 >> From: Kai Tietz <ktiet...@googlemail.com> >> Cc: binut...@sourceware.org, gdb-patc...@sourceware.org, >> gcc-patches@gcc.gnu.org >> >> > Btw, why do we need filename_dirchr? The use case for >> > filename_dirrchr is clear, but in what situations will we need the >> > other one? >> >> As the comment notes. strchr/strrchr searches for one character. This >> is for unix-file-system normally slash. On DOS based file-systems >> there are two characters representing a directory-separator. Slash and >> Backslash. Therefore this routine takes care that both are handled >> similiar to a single character searching. > > We are miscommunicating. I was asking when would a program want to > find the _first_ directory separator character in a file name. > Searching for the last one is a frequent use case: when you want to > create a file in the same directory as another, or when you are > looking for a basename of a file. But when do you need the first > slash?
See for example remote-fileio.c in remote_fileio_extract_ptr_w_len() as an example. There is more then one use-case. >> >> + if (!r || (r2 && r2 < r)) >> > >> > Why do you test for r2 being non-NULL? You are not going to >> > dereference it in the next comparison, and NULL is comparable as any >> > other value. >> >> As if we found slash, we don't want to override function's result by >> backslash not found. If the null-check wouldn't be present condition >> would be always true for r2 == NULL as, NULL is always less then a >> pointer. But r shall be modified only if r2 (backslash) was found >> before r (slash). >> (same logic but here from right to left for the strrchr-case) > > But in strrchr-case, r2 cannot be greater than r1 if it is NULL, > right? It can. It is a matter of signness of pointer comparision. Regards, Kai
