On Mon, 2010-11-01 at 20:56 +0200, Jani Monoses wrote:
> Is there a list of which compilers are supported and what versions
> recommeneded for building LO?
>
> I was thinking of the feasibility of using gcc's __builtin_constant_p in
> a macro to differentiate fast and not so fast paths for createFromAscii
> cases to keep the code uniform but still get the optimizations, but then
> figured that would not work with Visual Studio.
Well, it's always possible to hook off an ifdef of course. e.g.
#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ > 0)
__builtin_constant_p magic
#else
normal stuff
#endif
My first thought was that this would be ideal to at a minimum jam into
the existing RTL_CONSTASCII_USTRINGPARAM to detect if someone used
RTL_CONSTASCII_USTRINGPARAM with something unsuitable.
e.g. the attached test.c where gcc will give a compile error on the
invalid line 13, but will be ok on the valid line 12. Unfortunately
__builtin_choose_expr isn't available for c++ so g++ always barfs on
the .cxx example.
There's definitely merit in some sort of cunning around
__builtin_constant_p
C.
#include <stdio.h>
void foo(int i)
{
fprintf(stderr, "foo is %s\n", i == 1 ? "constant" : "impossible");
}
#define RTL_CONSTASCII_USTRINGPARAM(str) (__builtin_choose_expr(__builtin_constant_p(str), 1, (void)0))
int main(int argc, char *argv[]) {
const char *s = "ss";
foo(RTL_CONSTASCII_USTRINGPARAM("cc"));
foo(RTL_CONSTASCII_USTRINGPARAM(s));
return 0;
}
#include <stdio.h>
void foo(int i)
{
fprintf(stderr, "foo is %s\n", i == 1 ? "constant" : "impossible");
}
#define RTL_CONSTASCII_USTRINGPARAM(str) (__builtin_choose_expr(__builtin_constant_p(str), 1, (void)0))
int main(int argc, char *argv[]) {
const char *s = "ss";
foo(RTL_CONSTASCII_USTRINGPARAM("cc"));
foo(RTL_CONSTASCII_USTRINGPARAM(s));
return 0;
}
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