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It's maybe not quite what you're looking for, but Cforall's polymorphic functions can eliminate nearly-all the unsafety of void-pointer-based polymorphism at li

It's maybe not quite what you're looking for, but Cforall's polymorphic functions can eliminate nearly-all the unsafety of void-pointer-based polymorphism at little-to-no extra runtime cost (in fact, microbenchmarks in our as-yet-unpublished paper show speedup over void-pointer-based C in most cases due to more efficient generic type layout). As an example: forall(dtype T | sized(T)) T* malloc() { // in our stdlib return (T*)malloc(sizeof(T)); // calls libc malloc } int* i = malloc(); // infers T from return type

baybal2 9y ago
Excuse me for my lamerism, but can you tell me what is a polymorphic function? My idea was that if it is better to do as much compile time checks as possible before you introduce run-time checks. Does that void pointer protection run faster that code that was checked at compile time? How?
- BruceIV 9y ago
  A polymorphic function is one that can operate on different types[1]. You would maybe be familiar with them as template functions in C++, though where C++ compiles different versions of the template functions based on the parameters, we pass extra implicit parameters. The example above translates to something like the following in pure C: void* malloc_T(size_t sizeof_T, size_t alignof_T) { return malloc(sizeof_T); } int* i = (int*)malloc_T(sizeof(int), alignof(int)); In this case, since the compiler verifies that int is actually a type with known size (fulfilling `sized(T)`), it can generate all the casts and size parameters above, knowing they're correct. [1] To anyone inclined to bash my definition of polymorphism, I'm mostly talking about parametric polymorphism here, though Cforall also supports ad-hoc polymorphism (name-overloading). The phrasing I used accounts for both, and I simplified it for pedagogical reasons.

baybal2 9y ago

Excuse me for my lamerism, but can you tell me what is a polymorphic function? My idea was that if it is better to do as much compile time checks as possible before you introduce run-time checks. Does that void pointer protection run faster that code that was checked at compile time? How?

BruceIV 9y ago
A polymorphic function is one that can operate on different types[1]. You would maybe be familiar with them as template functions in C++, though where C++ compiles different versions of the template functions based on the parameters, we pass extra implicit parameters. The example above translates to something like the following in pure C: void* malloc_T(size_t sizeof_T, size_t alignof_T) { return malloc(sizeof_T); } int* i = (int*)malloc_T(sizeof(int), alignof(int)); In this case, since the compiler verifies that int is actually a type with known size (fulfilling `sized(T)`), it can generate all the casts and size parameters above, knowing they're correct. [1] To anyone inclined to bash my definition of polymorphism, I'm mostly talking about parametric polymorphism here, though Cforall also supports ad-hoc polymorphism (name-overloading). The phrasing I used accounts for both, and I simplified it for pedagogical reasons.