For example, wikipedia::article::format becomes:įor functions, this is then followed by the type information as format() is a void function, this is simply v hence:įor print_to, the standard type std::ostream (which is a typedef for std::basic_ostream >) is used, which has the special alias So a reference to this type is therefore RSo, with the complete name for the function being:
Name mangler sequence series#
For example, struct S Īll mangled symbols begin with _Z (note that an identifier beginning with an underscore followed by a capital letter is a reserved identifier in C, so conflict with user identifiers is avoided) for nested names (including both namespaces and classes), this is followed by N, then a series of pairs (the length being the length of the next identifier), and finally E. For example, it doesn't fully prevent errors like changes of data members of a struct or class. Mangling doesn't usually capture every detail of the calling process. Otherwise, incompatible calling conventions would be used, and most likely produce the wrong result or crash the program. Similarly, the linker will not be able to detect that the return type of f is different, and return an error. At link time the linker will detect there is no function f(int) and return an error. For example, functions int f() and int g(int) pure could be compiled into one object file, but then their signatures changed to float f() int g(int) and used to compile other source calling it.
These are more of a simplified error checking. An example of a language doing this is D. These stricter requirements needed to work with existing tools and conventions therefore, additional requirements were encoded in the name of the symbol, since that was the only information the traditional linker had about a symbol.Īnother use of name mangling is for detecting additional non-signature related changes, such as function purity, or whether it can potentially throw an exception or trigger garbage collection. These requirements enable method overloading and detection of some bugs (such as using different definitions of a function when compiling different source files). Later programming languages, like C++, defined stricter requirements for routines to be considered "equal", such as the parameter types, return type, and calling convention of a function. The simple programming languages of the 1970s, like C, only distinguished subroutines by their name, ignoring other information including parameter and return types. For example, to correctly link a function it needs its name, the number of arguments and their types, and so on. The linker needs a great deal of information on each program entity.
Name mangler sequence code#
It is required in these use cases because each signature might require different, specialized calling convention in the machine code.Īny object code produced by compilers is usually linked with other pieces of object code (produced by the same or another compiler) by a type of program called a linker. The need for name mangling arises where the language allows different entities to be named with the same identifier as long as they occupy a different namespace (typically defined by a module, class, or explicit namespace directive) or have different signatures (such as in function overloading). It provides a way of encoding additional information in the name of a function, structure, class or another datatype in order to pass more semantic information from the compiler to the linker. In compiler construction, name mangling (also called name decoration) is a technique used to solve various problems caused by the need to resolve unique names for programming entities in many modern programming languages. ( Learn how and when to remove this template message)
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