On May 5, 2012, at 2:56 PM, Leon Timmermans wrote: > On Sat, May 5, 2012 at 6:25 PM, Craig A. Berry <craigbe...@mac.com> wrote: >> Thanks for the suggestion. That might work, but might also fall afoul of >> the naked semicolon problem noted in the comment in perl.h: >> >> #define NOOP /*EMPTY*/(void)0 >> /* cea2e8a9dd23747f accidentally lost the comment originally from the first >> check in of thread.h, explaining why we need dNOOP at all: */ >> /* Rats: if dTHR is just blank then the subsequent ";" throws an error */ >> /* Declaring a *function*, instead of a variable, ensures that we don't rely >> on being able to suppress "unused" warnings. */ >> #define dNOOP extern int Perl___notused(void) >> >> But maybe that error would only happen with C and not C++? > > That's what he just said, it's only a problem when mixed statements > and declarations are not allowed. They are allowed in C99 and C++, but > not in C89. > >> The definition of dNOOP is an extremely well-trodden line of code with lots >> of changes demonstrating that anything that fixes a problem with it is >> highly likely to introduce one or more other problems. >> >> I don't actually understand why we need a dNOOP that's distinct from NOOP, >> i.e., why we can't just do: > > because: > > dNOOP; > int foo; > > Should work on a strict C89 compiler. That means that on such a > compiler, dNOOP must translate to a declaration. On a more lenient > compiler it doesn't matter what it compiles to (as long as it is a > no-op, obviously).
Thanks, Leon. Since I spend much of my time these days in vbscript and other perversions I do in fact need to be clobbered over the head with C basics sometimes, as you suspected. I simply hadn't remembered that a semicolon by itself was a statement, but I now see that C99 says, in section 6.8.3, "A null statement (consisting of just a semicolon) performs no operations." So Tony's suggestion should be fine, and we'll have plenty of time to smoke it thoroughly in 5.17. ________________________________________ Craig A. Berry mailto:craigbe...@mac.com "... getting out of a sonnet is much more difficult than getting in." Brad Leithauser
