On Wed, Oct 18, 2006 at 09:44:58PM +0200, Bruno Haible wrote: > > > How does what you need compare with the register_printf_function / > > > parse_printf_format facility in glibc's public header file <printf.h> ? > > > > Wow, I knew about register_printf_function, but I'd never noticed > > parse_printf_format before. > > But without the other part, which constructs the output string, this > function is useless to gdb, right? So there's no point in gnulib trying > to make a 100% glibc compatible parse_printf_format.
Right. > > printf breaks down into three stages: parsing the format string, > > recovering the arguments, and constructing the output string. We need > > completely normal versions of the first and third, but a non-va_arg > > based version of the second. > > Are you sure you can use the parsing stage and the output stage without > modifications? > - In the parsing phase, you need to recognize %lld also if the host > environment > doesn't support long longs (e.g. on MSVC hosts). This means the > #ifdef HAVE_LONG_LONG_INT > in printf-args.h needs to be adjusted for your use case. Yes, it looks like you're right. And, similar changes would have to be made to printf-parse.c. If we did this to the same copy, that would change the behavior of "%lld" on hosts which don't support long long; previously it would be handled as "long", and subsequently it would lead to an error in printf_fetchargs. Is that undesirable? > - In the output stage, when the host has 32-bit 'long's and the target > environment has 64-bit 'long's, the output routine that converts a > 'long' to decimal needs to be able to produce 20 decimal digits, not > just 10. No, I don't think I'd do it that way - it would be crazy, because it would have to rely on a different member of the arg union to hold the value, which would not fit otherwise. I was figuring I'd transform the result of printf-parse.c appropriately as I fetched the arguments. When presented with a "%ld" conversion that wouldn't work on the host, I'd adjust the flags to do a host "%lld" instead. I'm now worrying that I misunderstood how the gnulib vasnprintf works, though. This may be less useful than I thought, since it uses both the result of arg parsing and the format string :-( > - Also in the output stage, when you encounter a %ls directive with a > wide string argument, to you perform the wcstombs on the host machine > or on the target machine? To be honest, I don't particularly care about this today. GDB support for wide strings is miniscule and no one is improving it. However, if I were to support it, I would try to emulate the target machine's behavior on the host through some other mechanism. -- Daniel Jacobowitz CodeSourcery
