Noah Misch <noah@xxxxxxxxxxxxxx> writes: > That said, I'd like to fix it. Would one of the following be appropriate? > > 1) Change the test such that it creates truly invalid C in the false case. I > don't know how to do this, but perhaps a reader does. Ideas? Unfortunately there's no such thing as "truly invalid C", in the sense that every possible C compiler, whether conforming or not, will exit with nonzero status when asked to compile it. This is because people are free to add extensions. The best we can do is to write code that fails on all practical implementations. On the compilers in question, what value does 1/0 return? Perhaps we can make use of that somehow. Another possibility: perhaps these troublesome compilers reject arithmetic overflow? For example, do they reject the expression ((short int) 2147483647)? We could evaluate this expression in addition to 1/0. The reason I'm suggesting this is that the C standard requires a diagnostic for overflow, but not for division by zero (strange but true....). > 2) Test for the switch (including none) that makes the compiler > driver return a nonzero status when a division by zero exists in the > code. I'd rather not head down that path: it's too much maintenance hassle. How about this idea instead? 1. For native compiles, compile, link, and run a program that prints 1 or 0 depending on whether x is nonzero. This avoids the problem. 2. For cross-compiles, use the current strategy, but evaluate both 1/!x and 1/!!x. If both expressions compile, we have a troublesome compiler like HP's, so reject the compiler and abort the invocation of "configure". In the error message, suggest to the user that they find an option to make the compiler work right, and give the known flags as examples. 3. File a bug report with HP. 'static int x = 1/0;' should not compile by default. I'm surprised that it does, and I'll bet most other programmers are too. (Tell them that their current behavior is incompatible with Autoconf. :-) _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx http://lists.gnu.org/mailman/listinfo/autoconf
