libc-bottom-half/sources/__original_main.c

   1 #include <wasi/core.h>
   2 #include <wasi/libc.h>
   3 #include <stdlib.h>
   4 #include <sysexits.h>
   5
   6 // The user's `main` function, expecting arguments.
   7 int main(int argc, char *argv[]);
   8
   9 // If the user's `main` function expects arguments, the compiler won't emit
  10 // an `__original_main` function so this version will get linked in, which
  11 // initializes the argument data and calls `main`.
  12 __attribute__((weak))
  13 int __original_main(void) {
  14     __wasi_errno_t err;
  15
  16     // Get the sizes of the arrays we'll have to create to copy in the args.
  17     size_t argv_buf_size;
  18     size_t argc;
  19     err = __wasi_args_sizes_get(&argc, &argv_buf_size);
  20     if (err != __WASI_ESUCCESS) {
  21         _Exit(EX_OSERR);
  22     }
  23
  24     // Add 1 for the NULL pointer to mark the end, and check for overflow.
  25     size_t num_ptrs = argc + 1;
  26     if (num_ptrs == 0) {
  27         _Exit(EX_SOFTWARE);
  28     }
  29
  30     // Allocate memory for storing the argument chars.
  31     char *argv_buf = malloc(argv_buf_size);
  32     if (argv_buf == NULL) {
  33         _Exit(EX_SOFTWARE);
  34     }
  35
  36     // Allocate memory for the array of pointers. This uses `calloc` both to
  37     // handle overflow and to initialize the NULL pointer at the end.
  38     char **argv = calloc(num_ptrs, sizeof(char *));
  39     if (argv == NULL) {
  40         free(argv_buf);
  41         _Exit(EX_SOFTWARE);
  42     }
  43
  44     // Fill the argument chars, and the argv array with pointers into those chars.
  45     err = __wasi_args_get(argv, argv_buf);
  46     if (err != __WASI_ESUCCESS) {
  47         free(argv_buf);
  48         free(argv);
  49         _Exit(EX_OSERR);
  50     }
  51
  52     // Call main with the arguments!
  53     return main(argc, argv);
  54 }