Hi,
Jeff King wrote:
> I scoured the code base for cases of this, but it turns out
> that these two in git_config_set_multivar_in_file_gently()
> are the only ones. This case is actually quite interesting:
> we don't have a size_t, but rather use the subtraction of
> two pointers. Which you might think would be a signed
> ptrdiff_t, but clearly both gcc and clang treat it as
> unsigned (possibly because the conditional just above
> guarantees that the result is greater than zero).
Do you have more detail about this? I get worried when I read
something like this that sounds like a compiler bug.
C99 sayeth:
When two pointers are subtracted, both shall point to elements
of the same array object, or one past the last element of the
array object; the result is the difference of the subscripts
of the two array elements. The size of the result is
implementation-defined, and its type (a signed integer type)
is ptrdiff_t defined in the <stddef.h> header.
How can I reproduce the problem?
> We can avoid the whole question by just checking for a
> negative return value directly, as write_in_full() will
> never return any value except -1 or the full count.
>
> There's no addition to the test suite here, since you need
> to convince write() to fail in order to see the problem. The
> simplest reproduction recipe I came up with is to trigger
> ENOSPC (this only works on Linux, obviously):
Does /dev/full make it simpler to reproduce?
Thanks,
Jonathan
