implement perror

Cargo.lock

@@ -445,6 +445,7 @@ version = "0.1.0"
 dependencies = [
  "cbindgen 0.5.0",
  "platform 0.1.0",
+ "string 0.1.0",
  "va_list 0.1.0",
 ]
 

src/stdio/Cargo.toml

@@ -10,3 +10,4 @@ cbindgen = { path = "../../cbindgen" }
 [dependencies]
 platform = { path = "../platform" }
 va_list = { path = "../../va_list", features = ["no_std"] }
+string = { path = "../string" }

src/stdio/src/lib.rs

@@ -4,10 +4,13 @@
 
 extern crate platform;
 extern crate va_list as vl;
+extern crate string;
 
-use core::slice;
+use core::str;
+use core::fmt::Write;
 
 use platform::types::*;
+use platform::c_str;
 use vl::VaList as va_list;
 
 mod printf;
@@ -201,8 +204,14 @@ pub extern "C" fn pclose(stream: *mut FILE) -> c_int {
 }
 
 #[no_mangle]
-pub extern "C" fn perror(s: *const c_char) {
-    unimplemented!();
+pub unsafe extern "C" fn perror(s: *const c_char) {
+    let strerror = string::strerror(platform::errno);
+    let mut w = platform::FileWriter(2);
+    w.write_fmt(format_args!(
+        "{}: {}\n",
+        str::from_utf8_unchecked(c_str(s)),
+        str::from_utf8_unchecked(c_str(strerror))
+    ));
 }
 
 #[no_mangle]

tests/error.c

@@ -6,4 +6,5 @@
 int main(int argc, char** argv) {
     chdir("nonexistent");
     printf("errno: %d = %s\n", errno, strerror(errno));
+    perror("perror");
 }