For the code added in day 328, I've been trying to understand why gcc won't create usable code, it doesn't seem to like "va_list" pointers like ArgList.
The gcc error:
First it changes the (va_list *) type to (__va_list_tag *), I guess with a macro or something, but "__va_list_tag" isn't a real type, (it is built into gcc), so I can't cast to it. I can cast to (va_list *) and it will compile, but it will crash with a segmentation fault when I try to open "Profile" in the debug menu.
I'm not sure how to cast to a type with a [1] in it, does it mean an array of length 1? Does it need the length information or can you replace the [1] with an * in the cast? I couldn't get a cast to work with any form of [1] in it.
By not passing "ArgList" by reference, but by value, I can get it to compile and run normally, so I can only guess that gcc is doing something strange that prevents passing a "va_list" by reference.
I've included a link to the compiling/running mod in case it's unclear.
Thanks in advance to anyone who's more familiar with this stuff.
The gcc error:
1 2 3 4 | src/handmade_shared.h: In function ‘umm FormatStringList(umm, char*, char*, __va_list_tag*)’:
src/handmade_shared.h:388:84: error: cannot convert ‘__va_list_tag**’ to ‘__va_list_tag (*)[1]’
for argument ‘2’ to ‘s64 ReadVarArgSignedInteger(u32, __va_list_tag (*)[1])’
s64 Value = ReadVarArgSignedInteger(IntegerLength, &ArgList);
|
First it changes the (va_list *) type to (__va_list_tag *), I guess with a macro or something, but "__va_list_tag" isn't a real type, (it is built into gcc), so I can't cast to it. I can cast to (va_list *) and it will compile, but it will crash with a segmentation fault when I try to open "Profile" in the debug menu.
I'm not sure how to cast to a type with a [1] in it, does it mean an array of length 1? Does it need the length information or can you replace the [1] with an * in the cast? I couldn't get a cast to work with any form of [1] in it.
By not passing "ArgList" by reference, but by value, I can get it to compile and run normally, so I can only guess that gcc is doing something strange that prevents passing a "va_list" by reference.
I've included a link to the compiling/running mod in case it's unclear.
Thanks in advance to anyone who's more familiar with this stuff.
Yeah, this is an issue on 64-bit Intel architecture.
We already have this filed in github issues: https://github.com/HandmadeHero/cpp/issues/26
Here's an explanation why passing va_list by address is a problem: http://stackoverflow.com/a/8048892/675078
Correct way to do this is either to cast arglist to (va_list*) directly (because it is an array, and address of array is same as array) or to use va_copy to make a copy of va_list:
We already have this filed in github issues: https://github.com/HandmadeHero/cpp/issues/26
Here's an explanation why passing va_list by address is a problem: http://stackoverflow.com/a/8048892/675078
Correct way to do this is either to cast arglist to (va_list*) directly (because it is an array, and address of array is same as array) or to use va_copy to make a copy of va_list:
1 2 3 4 | va_list args_copy; va_copy(args_copy, args); OtherFunction(..., &args_copy); va_end(args_copy); |
Edited by Mārtiņš Možeiko
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