Hi Kjetil, On Dienstag, 7. Januar 2025 14:00:16 MEZ Kjetil Oftedal wrote:
How can the compiler in this case assume that endptr and str do not point to the same array object?
ISO C99 6.5,8 Relational operators 5) ... "If the expression P points to an element of an array object and the expression Q points to the last element of the same array object, the pointer expression Q+1 compares greater than P. In all other cases, the behavior is undefined"
How does the compiler at compile time know that endptr which is equivalent is to str[maxlen] is not within the range of string declared by str? Or in the terms of the above standard, how does it know that endptr is not Q+1?
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The compiler does not need to know! Let's consider the pointer 'x', the offset 'offs' and y = x + offset with y < x (because offset is huge). So if y < (x + offset) then y points to a different object by definition. Hence, the compiler is allowed to remove this test. Frank -- Dr.-Ing. Frank Mehnert, frank.mehnert@kernkonzept.com, +49-351-41 883 224 Kernkonzept GmbH. Sitz: Dresden. Amtsgericht Dresden, HRB 31129. Geschäftsführer: Dr.-Ing. Michael Hohmuth