Question

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C/C++: Optimization of pointers to string constants

Suppose you have a string "example" defined in a lot of places

// module1.h
char *x = "example";
// module2.h
char *a[] = { "text", "example" };
// module3.c
printf("example");
//etc.

Will this data will be duplicated or will the compiler makes only one reference to it?

Answer 1

It is implementation dependent. But that was the spirit of the immutable property of string literals.

Quoting from the C99 Rationale on string literals:

“String literals are not required to be modifiable. This specification allows implementations to share copies of strings with identical text, to place string literals in read-only memory, and to perform certain optimizations”