bunpen: bind execvpe

pkgs/additional/bunpen/rt/ext/exec.ha

@@ -1,10 +1,13 @@
 // vim: set shiftwidth=2 :
 
+use log;
+use os;
 use path;
 use rt;
+use strings;
 use types::c;
 
-export fn execve(path: str, argv: []str, envp: []str = []) (rt::errno | void) = {
+export fn execve(path: str, argv: []str, envp: []str = []) rt::errno = {
   let path_buf: [path::MAX]c::char = [0...];
 
   syscall(
@@ -14,6 +17,21 @@ export fn execve(path: str, argv: []str, envp: []str = []) (rt::errno | void) =
     to_cstr_array(argv): *[*]nullable *const c::char: uintptr: u64,
     to_cstr_array(envp): *[*]nullable *const c::char: uintptr: u64,
   )?;
+
+  log::fatal("[exec] unexpectedly returned without error");
+};
+
+// if `name` contains a slash, proceed as per `execve`.
+// otherwise, crawl $PATH and try executing until we succeed.
+export fn execvpe(name: str, argv: []str, envp: []str = []) rt::errno = {
+  return if (strings::contains(name, "/")) {
+    yield execve(name, argv, envp);
+  } else {
+    yield match (os::getenv("PATH")) {
+      case let p: str => yield _execvpe(p, name, argv, envp);
+      case void => yield execve(name, argv, envp);
+    };
+  };
 };
 
 // allocate and return a NULL-terminated array of pointers to c strings.
@@ -26,3 +44,19 @@ fn to_cstr_array(strs: []str) []nullable *const c::char = {
   append(cstrs, null);
   return cstrs;
 };
+
+// split `path` on `:`, crawl it, and try executing until we succeed.
+// note that 1:1 parity with libc's execvpe is probably not what we have here.
+fn _execvpe(path: str, name: str, argv: []str, envp: []str = []) rt::errno = {
+  let status = rt::ENOENT;
+  let pieces = strings::split(path, ":");
+  defer free(pieces);
+  for (let p .. pieces) {
+    let this_path = strings::join("/", p, name);
+    defer free(this_path);
+    status = execve(this_path, argv, envp);
+    // try the next item, or return the status if this is the last one.
+  };
+
+  return status;
+};