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https://git.proxmox.com/git/wasi-libc
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afbf94c39e
* Link `populate_args` only if we actually need command-line arguments. This avoids linking in the argv/argc initialization code, and the __wasi_args_sizes_get and __wasi_args_get imports, in programs that don't use command-line arguments. The way this works is, if the user writes `int main(int argc, char *argv[])`, the argument initialization code is loaded, and if they write `int main(void)`, it's not loaded. This promotes the `__original_main` mechanism into an effective contract between the compiler and libc, which wasn't its original purpose, however it seems to fit this purpose quite well. * Document that `__original_main` may be the user's zero-arg `main`.
54 lines
1.6 KiB
C
54 lines
1.6 KiB
C
#include <wasi/core.h>
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#include <wasi/libc.h>
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#include <stdlib.h>
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#include <sysexits.h>
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// The user's `main` function, expecting arguments.
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int main(int argc, char *argv[]);
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// If the user's `main` function expects arguments, the compiler won't emit
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// an `__original_main` function so this version will get linked in, which
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// initializes the argument data and calls `main`.
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int __original_main(void) {
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__wasi_errno_t err;
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// Get the sizes of the arrays we'll have to create to copy in the args.
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size_t argv_buf_size;
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size_t argc;
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err = __wasi_args_sizes_get(&argc, &argv_buf_size);
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if (err != __WASI_ESUCCESS) {
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_Exit(EX_OSERR);
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}
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// Add 1 for the NULL pointer to mark the end, and check for overflow.
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size_t num_ptrs = argc + 1;
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if (num_ptrs == 0) {
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_Exit(EX_SOFTWARE);
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}
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// Allocate memory for storing the argument chars.
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char *argv_buf = malloc(argv_buf_size);
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if (argv_buf == NULL) {
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_Exit(EX_SOFTWARE);
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}
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// Allocate memory for the array of pointers. This uses `calloc` both to
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// handle overflow and to initialize the NULL pointer at the end.
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char **argv = calloc(num_ptrs, sizeof(char *));
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if (argv == NULL) {
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free(argv_buf);
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_Exit(EX_SOFTWARE);
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}
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// Fill the argument chars, and the argv array with pointers into those chars.
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err = __wasi_args_get(argv, argv_buf);
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if (err != __WASI_ESUCCESS) {
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free(argv_buf);
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free(argv);
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_Exit(EX_OSERR);
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}
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// Call main with the arguments!
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return main(argc, argv);
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}
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