fix: reject opening directories as files in ext2 and fat32, add mbrtowc to libc

kernel/src/Api/BuildNo.hpp

@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 182
+#define MONTAUK_BUILD_NUMBER 184

kernel/src/Fs/Ext2.cpp

@@ -1202,6 +1202,13 @@ namespace Fs::Ext2 {
         Inode inode;
         if (!TraversePath(self, path, &inodeNum, &inode)) return -1;
 
+        // Directories are not openable as files, matching the ramdisk. A
+        // handle on one would fail every read/write anyway, and userspace
+        // stat() falls back to open() when it cannot get real metadata:
+        // succeeding here classified every directory as a regular file and
+        // GCC's include-path setup then rejected them as "not a directory".
+        if ((inode.i_mode & IMODE_TYPE_MASK) == IMODE_DIR) return -1;
+
         for (int i = 0; i < MaxFilesPerInstance; i++) {
             if (!self.files[i].inUse) {
                 self.files[i].inUse = true;

kernel/src/Fs/Fat32.cpp

@@ -955,6 +955,10 @@ namespace Fs::Fat32 {
         ParsedEntry entry;
         if (!TraversePath(inst, path, &entry)) return -1;
 
+        // Directories are not openable as files; see the matching note in
+        // Ext2::OpenImpl (userspace stat() falls back to open()).
+        if ((entry.attributes & ATTR_DIRECTORY) != 0) return -1;
+
         // Find a free file handle
         auto& self = g_instances[inst];
         for (int i = 0; i < MaxFilesPerInstance; i++) {

programs/include/libc/wchar.h

@@ -21,6 +21,7 @@ typedef struct {
 /* Byte-oriented C locale only: one byte, one character. */
 size_t mbstowcs(wchar_t *dst, const char *src, size_t n);
 int    mblen(const char *s, size_t n);
+size_t mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *ps);
 
 #ifdef __cplusplus
 }

programs/lib/libc/libc.c

@@ -25,6 +25,7 @@
 #include <sys/mman.h>
 #include <sys/time.h>
 #include <unistd.h>
+#include <wchar.h>
 
 /* ========================================================================
    Raw syscall wrappers (C versions matching kernel ABI)
@@ -3622,6 +3623,20 @@ int mbtowc(wchar_t *pwc, const char *s, size_t n) {
     return 1;
 }
 
+/* Restartable form of mbtowc. The C locale carries no shift state, so ps is
+   ignored; binutils reaches for this once configure sees mbstate_t. */
+size_t mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *ps) {
+    (void)ps;
+    if (s == NULL) return 0;         /* query: the C locale is stateless */
+    if (n == 0) return (size_t)-2;   /* incomplete: no bytes to examine */
+    if (*s == '\0') {
+        if (pwc != NULL) *pwc = 0;
+        return 0;
+    }
+    if (pwc != NULL) *pwc = (wchar_t)(unsigned char)*s;
+    return 1;
+}
+
 int wctomb(char *s, wchar_t wc) {
     if (s == NULL) return 0;
     *s = (char)wc;