Hi,
On Mon, 18 Apr 2016, Vladimir Vissoultchev wrote:
'#if PATHCMP==stricmp' doesn't do what you want anyway. The preprocessor
== can't
compare strings, so the above is always true (because no matter if PATHCMP
is
defined to stricmp or not defined it evaluates to zero, and as stricmp is
no macro
it evaluates to zero as well).
Btw, had some time to do a test with this snippet:
#define PATHCMP stricmp
#if PATHCMP==stricmp
#error Michael is wrong
#else
#error Michael is right
#endif
and got these results:
C:> tcc -c test.c
test.c:4: error: #error Michael is wrong
C:> gcc -c test.c
test.c:4:6: error: #error Michael is wrong
#error Michael is wrong
^
No, Michael is right. I said "no matter if PATHCMP is defined to stricmp
(or any other string) or not defined at all, the conditional will always
evaluate to true". You proved one side, for the other part:
$ cat x.c
#if PATHCMP==foobar
Michael is right
#endif
$ gcc -E x.c
...
Michael is right
$ gcc -E -DPATHCMP=blaeh x.c
...
Michael is right
$ tcc -E x.c
Michael is right
$ tcc -E -DPATHCMP=blaeh x.c
Michael is right
So, your conditional wasn't actually a conditional at all.
This surprises me a lot, as I thought it was only VS that was being
"clever" and had me tricked here.
Probably this was impl as an extension by some version of gcc onwards or
is it part of the standard now?
No. It's per standard. An undefined token evaluates to zero in
preprocessor conditionals. A token defined to some other token evaluates
to whatever that token evaluates (in the above, because "blaeh" and
"foobar" aren't defined, to zero).
Does that clear it up?
Ciao,
Michael.
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