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As per book The C++ Programming Language (Bjarne Stroustrup), in section 15.2.3 (The One definition rule) page no 425, I write program as below :
file1.cpp
struct S2 { int a; char b; };
file2.cpp
struct S2 { int a; char bb; };
int main(){ return 0;}
To compile I tried below command.
g++ -std=c++11 file1.cpp file2.cpp
and
clang++ -std=c++11 file1.cpp file2.cpp
Both these command producing executable with out any error or warning. But as per book this example should give error.
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Yes, that is perfectly fine.
A previously defined identifier (tag) can be used to refer to a structure type defined elsewhere. In this case, struct-declaration-list cannot be repeated as long as the definition is visible.
Yes, you can assign one instance of a struct to another using a simple assignment statement. In the case of non-pointer or non pointer containing struct members, assignment means copy. In the case of pointer struct members, assignment means pointer will point to the same address of the other pointer.
A nested structure in C is a structure within structure. One structure can be declared inside another structure in the same way structure members are declared inside a structure.
One Definition Rule says that:
if one .cpp file defines
struct S { int x; };and the other .cpp file definesstruct S { int y; };, the behavior of the program that links them together is undefined.
So, your program invokes undefined behaviour (UB). So, compiler isn't required to give diagnosis for this.
If you want know the reason behind it then read this.
Hope it helps. :)
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