Thank you very much. I misunderstood the document. Bingfeng
> -----Original Message----- > From: Jonathan Wakely [mailto:jwakely....@gmail.com] > Sent: 04 October 2011 12:48 > To: Bingfeng Mei > Cc: gcc@gcc.gnu.org > Subject: Re: Not conform to c90? > > On 4 October 2011 12:09, Bingfeng Mei wrote: > > Hello, > > According to http://gcc.gnu.org/onlinedocs/gcc-4.6.1/gcc/Zero- > Length.html#Zero-Length > > A zero-length array should have a length of 1 in c90. > > I think you've misunderstood that page. You cannot have a zero-length > array in C90, what that page says is that in strict C90 you would have > to create an array of length 1 as a workaround. It's not saying > sizeof(char[0]) is 1. > > GNU C an C99 allow you to have a zero-length array. > > > But I tried > > > > struct > > { > > char a[0]; > > } ZERO; > > > > void main() > > { > > int a[0]; > > printf ("size = %d\n", sizeof(ZERO)); > > } > > > > Compiled with gcc 4.7 > > ~/work/install-x86/bin/gcc test.c -O2 -std=c90 > > > > size = 0 > > If you add -pedantic you'll discover that program isn't valid in C90. > > > I noticed the following statement in GCC document. > > "As a quirk of the original implementation of zero-length arrays, > > sizeof evaluates to zero." > > > > Does it mean GCC just does not conform to c90 in this respect? > > C90 doesn't allow zero length arrays, so you're trying to evaluate a > GNU extension in terms of a standard. I'm not sure what you expect to > happen.
