libc: Propagate errors correctly in shadow functions

libc/include/stdio.h

@@ -56,7 +56,7 @@ extern "C"
 #endif
 
     /* Flush a stream's buffers. */
-    int fflush(FILE*);
+    int fflush(FILE* stream);
 
     /* Open a file and bind a stream to it. */
     FILE* fopen(const char* path, const char* mode);
@@ -67,7 +67,7 @@ extern "C"
     /* Change the underlying file and mode of a stream. */
     FILE* freopen(const char* path, const char* mode, FILE* stream);
 
-    /* Close a file and frees up its stream. */
+    /* Close a file and free up its stream. */
     int fclose(FILE* stream);
 
     /* Return the file descriptor associated with a stream. */

libc/src/shadow.cpp

@@ -16,7 +16,7 @@ extern "C"
     {
         struct spwd* result;
 
-        getspent_r(&spwd, s_buf, sizeof(s_buf), &result);
+        if (getspent_r(&spwd, s_buf, sizeof(s_buf), &result) < 0) return nullptr;
 
         return result;
     }
@@ -28,7 +28,7 @@ extern "C"
         if (!f)
         {
             f = fopen("/etc/shadow", "r");
-            if (!f) return 0;
+            if (!f) return -1;
             fcntl(fileno(f), F_SETFD, FD_CLOEXEC);
         }
 

libc/src/stdio.cpp

@@ -793,11 +793,13 @@ extern "C"
             {
                 close(pfds[0]);
                 dup2(pfds[1], STDOUT_FILENO);
+                close(pfds[1]);
             }
             else
             {
                 close(pfds[1]);
                 dup2(pfds[0], STDIN_FILENO);
+                close(pfds[0]);
             }
 
             execl("/bin/sh", "sh", "-c", command, nullptr);