On Fri, 3 Mar 2023 at 18:14, Tom Lane <t...@sss.pgh.pa.us> wrote: > Jeroen Vermeulen <jtv...@gmail.com> writes: > > On Fri, 3 Mar 2023 at 17:33, Tom Lane <t...@sss.pgh.pa.us> wrote: > >> Let's not do that. Declare it const char *, or maybe better const void > *. > > > Personally I would much prefer "char" over "void" here: > > * It really is a char buffer, containing text. > > Not in binary-mode COPY. >
True. And in that case zero-termination doesn't matter much either. But overall libpq's existing choice seems reasonable. > As for const, I would definitely have preferred that. But if the caller > > needs a zero-terminated string, forcing them into a memcpy() would kind > of > > defeat the purpose. > > I'm willing to grant that avoiding malloc-and-free is worth the trouble. > I'm not willing to allow applications to scribble on libpq buffers to > avoid memcpy. Even your not-a-patch patch fails to make the case that > this is essential, because you could have used fwrite() instead of > printf() (which would be significantly faster yet btw, printf formatting > ain't cheap). > Your house, your rules. For my own use-case "const" is just peachy. The printf() is just the simplest example that sprang to mind though. There may be other use-cases out there involving libraries that require zero-terminated strings, and I figured an ability to set a sentinel could help those. > Can do that, sure. I'll also try benchmarking a variant that doesn't take > > a callback at all, but gives you the buffer pointer in addition to the > > size/status return. I don't generally like callbacks. > > Um ... that would require an assumption that libpq neither changes nor > moves that buffer before returning to the caller. I don't much like > that either. > Not an assumption about _before returning to the caller_ I guess, because the function would be on top of that anyway. The concern would be libpq changing or moving the buffer _before the caller is done with the line._ Which would require some kind of clear rule about what invalidates the buffer. Yes, that is easier with the callback. Jeroen
