HCoop / hcoop / debian / mlton.git / blame
| Commit | Line | Data |
|---|---|---|
| 7f918cf1 CE |
1 | CallingFromSMLToC |
| 2 | ================= | |
| 3 | ||
| 4 | MLton's <:ForeignFunctionInterface:> allows an SML program to _import_ | |
| 5 | C functions. Suppose you would like to import from C a function with | |
| 6 | the following prototype: | |
| 7 | [source,c] | |
| 8 | ---- | |
| 9 | int foo (double d, char c); | |
| 10 | ---- | |
| 11 | MLton extends the syntax of SML to allow expressions like the following: | |
| 12 | ---- | |
| 13 | _import "foo": real * char -> int; | |
| 14 | ---- | |
| 15 | This expression denotes a function of type `real * char -> int` whose | |
| 16 | behavior is implemented by calling the C function whose name is `foo`. | |
| 17 | Thinking in terms of C, imagine that there are C variables `d` of type | |
| 18 | `double`, `c` of type `unsigned char`, and `i` of type `int`. Then, | |
| 19 | the C statement `i = foo (d, c)` is executed and `i` is returned. | |
| 20 | ||
| 21 | The general form of an `_import` expression is: | |
| 22 | ---- | |
| 23 | _import "C function name" attr... : cFuncTy; | |
| 24 | ---- | |
| 25 | The type and the semicolon are not optional. | |
| 26 | ||
| 27 | The function name is followed by a (possibly empty) sequence of | |
| 28 | attributes, analogous to C `__attribute__` specifiers. | |
| 29 | ||
| 30 | ||
| 31 | == Example == | |
| 32 | ||
| 33 | `import.sml` imports the C function `ffi` and the C variable `FFI_INT` | |
| 34 | as follows. | |
| 35 | ||
| 36 | [source,sml] | |
| 37 | ---- | |
| 38 | sys::[./bin/InclGitFile.py mlton master doc/examples/ffi/import.sml] | |
| 39 | ---- | |
| 40 | ||
| 41 | `ffi-import.c` is | |
| 42 | ||
| 43 | [source,c] | |
| 44 | ---- | |
| 45 | sys::[./bin/InclGitFile.py mlton master doc/examples/ffi/ffi-import.c] | |
| 46 | ---- | |
| 47 | ||
| 48 | Compile and run the program. | |
| 49 | ---- | |
| 50 | % mlton -default-ann 'allowFFI true' -export-header export.h import.sml ffi-import.c | |
| 51 | % ./import | |
| 52 | 13 | |
| 53 | success | |
| 54 | ---- | |
| 55 | ||
| 56 | ||
| 57 | == Download == | |
| 58 | * <!RawGitFile(mlton,master,doc/examples/ffi/import.sml)> | |
| 59 | * <!RawGitFile(mlton,master,doc/examples/ffi/ffi-import.c)> | |
| 60 | ||
| 61 | ||
| 62 | == Next Steps == | |
| 63 | ||
| 64 | * <:CallingFromSMLToCFunctionPointer:> |