Dear List,
Eric Blake wrote:
> your check for sigsetjmp was violating
> POSIX and creating an invalid C program (you can't take the address of an
> array, only an array element).
The patch looks correct to me - the correct type of the parameter is
"pointer to the
element type of the array type sigjmp_buf". The statement about array
addresses,
however, is certainly wrong. Of course one can take the address of an
array! One
can take the address of any object not explicitly declared with
storage-class "register".
Mr. Blake perhaps suspects that there is a discrepancy in the depth of
referencing
(sometype * vs. sometype **). His line about "not taking the address of
an array"
suggests strongly that he thinks there is, and that "&bf" must be a
pointer to some
mysterious, floating, address-less reference to the array. In fact,
it's merely a pointer
to the array, with no intermediate anything.
The address of the first element of the sigjump_buf array (which is what
will be
passed if "bf" is used) is necessarily the same as the address of the
array as a whole
(which will be passed if "&bf" is used). C requires this: one MUST be
able to get at
the members of an array by indexing!
There's a certain amount of freedom in deciding how to represent
pointers internally,
but I don't believe that it extends to giving different pointer
representations for &bf and
&bf[0], even though they are of different types. If the compiler
doesn't actually gag at
the point where the call is made (and the patch is applied) the effect
is the same. The
compiler is not required to gag, and in my experience compilers will
only do so if all
warnings are treated as errors. Of course, if the argument ever reaches
sigsetjmp() ,
it will be implicitly coerced to whatever type sigsetjmp() expects.
Bernard Leak.
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