Ian Lance Taylor <ian@airs.com> writes:
| Gabriel Dos Reis <[EMAIL PROTECTED]> writes:
|
| > Does GCC support any target where the object representation of a
| > fundamental type T (e.g. int, float, double, pointers) whose all bits
| > are zero does not hold value (T)0?
|
| Surprisingly, the answer seems to be yes.
Oh gosh.
| For the C4X target, a
| single precision floating point zero is apparently represented as
| 0x80000000 (for double precision there is another 32 zero bits).
Very interesting.
| That said, it doesn't actually work correctly. Compiling
|
| float f;
| float g = 0.0;
| struct s { int i; float f; int j; };
| struct s sv = { 1, 0.0, 2 };
|
| gives me
|
| .file "foo.c"
| .version 40
|
| .data
| data_sec:
| .global _g
| .globl _g
| .bss _g,1
| .global _sv
| .data
| _sv:
| .word 1
| .word -2147483648
| .word 2
| .globl _f
| .bss _f,1
| .end
|
| In other words, the floating point zero is only generated correctly
| when gcc is forced to output the initializer for some other reason.
I guess, this is not something C4X maintainers will correct in the future?
| Given that doesn't work, it is probably reasonably safe to assume gcc
| is always going to generate all zero bits for a fundamental types
| initialized to zero.
OK, thanks. I was rewriting part of valarray and I saw I made that
assumption, and since it is bug chasing time I thought I should make
sure my use of memset() isn't going to bomb out.
-- Gaby
