libc: Implement strerror()

libs/libc/include/string.h

@@ -23,6 +23,8 @@ extern "C"
     deprecated("strcat is unsafe and should not be used; use strncat instead") char* strcat(char*, const char*);
     char* strncat(char*, const char*, size_t);
 
+    char* strerror(int);
+
 #ifdef __cplusplus
 }
 #endif

libs/libc/src/string.cpp

@@ -1,3 +1,4 @@
+#include <errno.h>
 #include <luna.h>
 #include <string.h>
 
@@ -108,4 +109,20 @@ extern "C"
         // we return "m_start" + the amount of bytes that were transfered
         return (void*)(((size_t)start) + i);
     }
+
+#pragma GCC push_options
+#pragma GCC diagnostic ignored "-Wwrite-strings"
+
+    char* strerror(int errnum)
+    {
+        switch (errnum)
+        {
+        case EPERM: return "Operation not permitted";
+        case EINVAL: return "Invalid argument";
+        case ENOMEM: return "Out of memory";
+        default: return 0;
+        }
+    }
+
+#pragma GCC pop_options
 }