How Can I Correctly Allocate Memory for Structures Containing std::strings in C ?

Handling Structures with std::Strings in C : Navigating Memory Allocation

In C , when dealing with structures containing std::strings and utilizing malloc(), certain pitfalls can arise. Consider the following example:

struct example {
 std::string data;
};

int main() {
 example *ex = (example *)malloc(sizeof(*ex));
 ex->data = "hello world";
 std::cout << ex->data << std::endl;
}

Upon execution, this program crashes with a segmentation fault. This behavior stems from the inherent nature of malloc() and the construction of std::strings.

Maldvertising and Memory Allocation

Unlike new, malloc() merely allocates raw memory. In this context, attempting to use malloc()-ed memory as a "real" object can lead to undefined results. To correctly instantiate objects in memory, use new instead of malloc():

example *ex = new example;

Tricking malloc() into Cooperation

Alternatively, by using a combination of malloc() and the placement new operator, it is feasible to construct objects in malloc()-ed memory:

void *ex_raw = malloc(sizeof(example));
example *ex = new(ex_raw) example;

However, employing these techniques may prove unnecessary in the context of managing structures with std::strings.

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