http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58387
--- Comment #17 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- On Fri, 13 Sep 2013, su at cs dot ucdavis.edu wrote: > I noticed a stackoverflow discussion on this very topic: > > http://stackoverflow.com/questions/7961067/how-undefined-is-undefined-behavior > That doesn't really seem to get into the distinction that in some cases where the C standard says something is undefined, what it says is undefined is a property of an execution of a program, while in some cases it's a property of the program itself. In the case discussed there, the undefinedness is a property of an execution of the program, but in some cases (e.g. where one translation unit contains the declaration "extern int i;" and another contains "extern char i;") it's a property of the program. You need to read the C standard carefully in each case to work out which it is.
