Hi, On Thu, 6 Mar 2008, Reece Dunn wrote: > On 06/03/2008, Johannes Schindelin <Johannes.Schindelin@xxxxxx> wrote: > > > On Thu, 6 Mar 2008, Reece Dunn wrote: > > > > > On 06/03/2008, Mike Hommey <mh@xxxxxxxxxxxx> wrote: > > > > On Thu, Mar 06, 2008 at 02:14:43AM +0100, Johannes Schindelin wrote: > > > > > > > > > > The most common use of addf() was to init a strbuf and addf() > > > > > right away. Since it is so common, it makes sense to have a > > > > > function strbuf_initf() to wrap both calls into one. > > > > > > > > > > Unfortunately, C (and cpp) has no way to make this easy > > > > > without code duplication, as we need to va_init() in > > > > > strbuf_addf() possibly a few times. So the code for addf() is > > > > > copied. Fortunately, the code is pretty short, so not too > > > > > much had to be copied as-is. > > > > > > Why not have a strbuf_vaddf and strbuf_vinitf that take a va_arg as > > > a parameter. This would mean that you don't have code duplication, > > > and it is flexible enough if you want to add more customisations in > > > the future. No macro needed. This is what the printf/scanf family > > > of functions do. > > Is it possible to pass a void * to a strbuf_vaddf function that you can > pass to va_start, so you can then restart the va_list? AFAIU va_list() works on the stack (on less register-challenged systems than x86, the first parameters are possibly passed as registers, too, but it has to resort to the stack at a certain number of parameters). Since the stack is also used (at least on register-challenged yadda yadda) to store the return address, va_list() would most likely pick that up, too. Now, that just _might_ still work, since the printf() family determines the number of arguments from the format string. But then there are machines which are _not_ completely stack-based, for example SPARC. IIRC the first 8 parameters are passed by a so-called register window, which changes with each function call. So no, I think there is no portable way to pass them around. Of course, having a simple implementation for addf() _not_ using vsnprintf() could help, too (and make the process more efficient, probably). I thought. The formats we'd have to support are: $ git grep strbuf_addf | sed -e 's/^[^"]*"\([^"]*\)".*$/\1/' -e 's/%%//g' -e 's/%/\ &/g' | sed -n -e 's/\(%[^a-zA-Z]*[a-zA-Z]\).*/\1/p' | sort | uniq %02X %06o %c %d %l %o %s %.*s %u So it does not look too bad. 'X', 'o', 'd', 'l' and 'u', possibly with a size specifier (left 0-padded), 'c' and 's' (possibly with a length parameter). The implementation wouldn't be _too_ short, I'd say, but doable. Ciao, Dscho -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
