libc-bottom-half/sources/__main_void.c

   1 #include <wasi/api.h>
   2 #include <stdlib.h>
   3 #include <sysexits.h>
   4
   5 // The user's `main` function, expecting arguments.
   6 int __main_argc_argv(int argc, char *argv[]);
   7
   8 // If the user's `main` function expects arguments, the compiler will rename
   9 // it to `__main_argc_argv`, and this version will get linked in, which
  10 // initializes the argument data and calls `__main_argc_argv`.
  11 __attribute__((weak, nodebug))
  12 int __main_void(void) {
  13     __wasi_errno_t err;
  14
  15     // Get the sizes of the arrays we'll have to create to copy in the args.
  16     size_t argv_buf_size;
  17     size_t argc;
  18     err = __wasi_args_sizes_get(&argc, &argv_buf_size);
  19     if (err != __WASI_ERRNO_SUCCESS) {
  20         _Exit(EX_OSERR);
  21     }
  22
  23     // Add 1 for the NULL pointer to mark the end, and check for overflow.
  24     size_t num_ptrs = argc + 1;
  25     if (num_ptrs == 0) {
  26         _Exit(EX_SOFTWARE);
  27     }
  28
  29     // Allocate memory for storing the argument chars.
  30     char *argv_buf = malloc(argv_buf_size);
  31     if (argv_buf == NULL) {
  32         _Exit(EX_SOFTWARE);
  33     }
  34
  35     // Allocate memory for the array of pointers. This uses `calloc` both to
  36     // handle overflow and to initialize the NULL pointer at the end.
  37     char **argv = calloc(num_ptrs, sizeof(char *));
  38     if (argv == NULL) {
  39         free(argv_buf);
  40         _Exit(EX_SOFTWARE);
  41     }
  42
  43     // Fill the argument chars, and the argv array with pointers into those chars.
  44     // TODO: Remove the casts on `argv_ptrs` and `argv_buf` once the witx is updated with char8 support.
  45     err = __wasi_args_get((uint8_t **)argv, (uint8_t *)argv_buf);
  46     if (err != __WASI_ERRNO_SUCCESS) {
  47         free(argv_buf);
  48         free(argv);
  49         _Exit(EX_OSERR);
  50     }
  51
  52     // Call `__main_argc_argv` with the arguments!
  53     return __main_argc_argv(argc, argv);
  54 }