Free C-malloc()'d memory in Swift?

Question

I\'m using the Swift compiler\'s Bridging Header feature to call a C function that allocates memory using malloc(). It then returns a pointer to that memory. Th

Answer 1

Swift does not manage memory that is allocated with malloc(), you have to free the memory eventually:

let ret = the_function("something") // returns pointer to malloc'ed memory
let str = String.fromCString(ret)!  // creates Swift String by *copying* the data
free(ret) // releases the memory

println(str) // `str` is still valid (managed by Swift)

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Note that a Swift String is automatically converted to a UTF-8 string when passed to a C function taking a const char * parameter as described in String value to UnsafePointer<UInt8> function parameter behavior. That's why

let ret = the_function(("something" as NSString).UTF8String)

can be simplified to

let ret = the_function("something")