------- Comment #30 from rogerio at rilhas dot com 2010-08-11 20:58 ------- Really? Your comment #11 has so many mistakes in it that maybe you are the one who should learn a little bit more on C.
>The ABI is not of concern here really. The issue comes down to you have: >char *a; >char **b = &a; >use(b[1]); This comment just means you missed the point. Maybe you just memorized the C standar, maybe not, but you didn't understand that I was doing something different. Did you miss the part in my comment #14 where I mentioned that &a does not point to only 4 bytes but, instead, 16 bytes? Didn«t you understand the equivalent code would be: char* a[4]; char **b =&a[0]; use(b[1]); Didn't you realize that there is nothing wrong with this code? Its basic C. The code does not work because GCC is not doing its job right, otherwise, by cdecl definition, there would a would be an array of 4 pointers, like I showed. It seems you didn't understand, but it is, in fact, quite simple. Check what cdecl means, then you will realize that the 4 parameters are supposed to be equivalent to char* a[4]. Nothing else I can do here, really, if you don«t understand this then maybe you should be responsible for answering to comments on such an important project as GCC. >It is undefined what happens when you access b[1]. It does not matter if the >ABI defines that the arguments are passed via the stack in ascending order or >not. It could pass them via descending order. Accessing an out of bounds >array is causing the issue here. This is very wrong again. Don«t hide in out of bounds array. The point is exactly that, you are wrong about what the problem is. The problem is that the address GCC gives me is not to the 4 packed parameters, not the out of bounds. If GCC packed the 4 entries there would be no out of bounds problem. Maybe you need to learn C, I did learn it and well, so I know what a pointer does and what happens when you go out of bounds. So the problem is the underlying buffer of data created by GCC is bad, not that I use the 1-entry pointer to an array to access the following elements. You are just wrong, and I seem to be unable to make you see just how wrong you are. >This is not about GCC vs MS Visual studio issue, this is a C/C++ standard issue >saying what you are doing is undefined. Can you quote some part of the standard to back up your claims? I did backup my claims, you have not yet backed up yours. >Another thing well defined in C is what happens when navigating an array out of its bounds. Kinda, you can go one past the array bounds for the address but you cannot access it. That is what the C/C++ standard says. I can quote the standard if needed. Anything else is undefined. You are just wrong again. char* a[4]; char** b=&a[0]; access(b[0], b[1], b[2], b[3]). This code is valid although b is a pointer to one and only one address. This is the example in my code (assuming cdecl), you can try to avoid it, and compare to wrong code like you did in comment #11, but that will not be helpful to the GCC project, you will just keep wasting resources. So, as you can see, there is nothing correct about your comment #11. Should't you be reading something somewhere then? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45249
