diff --git a/include/errno.h b/include/errno.h
index bf96a81..ce7770d 100644
--- a/include/errno.h
+++ b/include/errno.h
@@ -27,36 +27,37 @@
 
 //----------------------------------------------------------------------------//
 
-#ifndef _eentry
-#define _estart                 enum {
-#define _eentry(code, desc)         code,
-#define _eentry(code, desc)         code,
-#define _eend                   _EMAX };
+#ifndef _EENTRY
+#define _ESTART                     enum {
+#define _EENTRY(code, num, desc)         code = num,
+#define _EEND                       };
 #endif
 
-_estart
-_eentry(EOK,            "No error")
-_eentry(EPERM,          "Operation not permitted")
-_eentry(ENOENT,         "No such entry, file, or directory")
-_eentry(ESRCH,          "No such process or thread")
-_eentry(EINTR,          "Operation interrupted")
-_eentry(EIO,            "I/O error")
-_eentry(ENXIO,          "No such device or address")
-_eentry(E2BIG,          "List too long")
-_eentry(ENOEXEC,        "Not an executable format")
-_eentry(EBADF,          "Bad file, fd, or stream")
-_eentry(EAGAIN,         "Try again")
-_eentry(ENOMEM,         "Not enough memory")
-_eentry(EINVAL,         "Invalid argument value")
-_eentry(ENOSYS,         "Functionality not implemented")
-_eentry(EADDRINUSE,     "Address in use")
-_eentry(EFAILED,        "Failure (unspecified reason)")
-_eentry(EALIGN,         "Alignment error or fault")
-_eentry(EENDF,          "End of file or stream")
-_eend
+_ESTART
+_EENTRY(EOK,            -0,     "No error")
+_EENTRY(EPERM,          -1,     "Operation not permitted")
+_EENTRY(ENOENT,         -2,     "No such entry, file, or directory")
+_EENTRY(ESRCH,          -3,     "No such process or thread")
+_EENTRY(EINTR,          -4,     "Operation interrupted")
+_EENTRY(EIO,            -5,     "I/O error")
+_EENTRY(ENXIO,          -6,     "No such device or address")
+_EENTRY(E2BIG,          -7,     "List too long")
+_EENTRY(ENOEXEC,        -8,     "Not an executable format")
+_EENTRY(EBADF,          -9,     "Bad file, fd, or stream")
+_EENTRY(EAGAIN,         -10,    "Try again")
+_EENTRY(ENOMEM,         -11,    "Not enough memory")
+_EENTRY(EINVAL,         -12,    "Invalid argument value")
+_EENTRY(ENOSYS,         -13,    "Functionality not implemented")
+_EENTRY(EADDRINUSE,     -14,    "Address in use")
+_EENTRY(EFAILED,        -15,    "Failure (unspecified reason)")
+_EENTRY(EALIGN,         -16,    "Alignment error or fault")
+_EENTRY(EENDF,          -17,    "End of file or stream")
+_EENTRY(_EMAX,          -18,    "... min error id ...")
+_EEND
 
-#undef _estart
-#undef _eentry
-#undef _eend
+#undef _ESTART
+#undef _EENTRY
+#undef _EEND
 
 #endif
+
diff --git a/include/libc.h b/include/libc.h
index 5e65eaf..84d5836 100644
--- a/include/libc.h
+++ b/include/libc.h
@@ -51,7 +51,7 @@ typedef unsigned long       uintptr_t;
 typedef signed long         intmax_t;
 typedef unsigned long       uintmax_t;
 
-typedef uint                error_t;
+typedef int                 error_t;
 typedef __builtin_va_list   va_list;
 
 //----------------------------------------------------------------------------//
@@ -336,7 +336,7 @@ static_assert(sizeof(void *) == 8, _SA_MSG);
 #define atomic_xadd(P, V)           __sync_fetch_and_add((P), (V))
 #define atomic_cmpxchg(P, O, N)     __sync_val_compare_and_swap((P), (O), (N))
 #define atomic_inc(P)               __sync_add_and_fetch((P), 1)
-#define atomic_dec(P)               __sync_add_and_fetch((P), -1) 
+#define atomic_dec(P)               __sync_add_and_fetch((P), -1)
 #define atomic_add(P, V)            __sync_add_and_fetch((P), (V))
 #define atomic_set_bit(P, V)        __sync_or_and_fetch((P), 1<<(V))
 #define atomic_clear_bit(P, V)      __sync_and_and_fetch((P), ~(1<<(V)))
diff --git a/kaleid/kernel/io/keyb.c b/kaleid/kernel/io/keyb.c
index d78fcd0..fc3fcaf 100644
--- a/kaleid/kernel/io/keyb.c
+++ b/kaleid/kernel/io/keyb.c
@@ -40,11 +40,11 @@ static bool shiftPressed = 0;
 static bool controlPressed = 0;
 
 static void KeybPrint(uchar _code)
-{    
+{
     uint code = (uint)_code;
 
     const uint *table;
-    
+
     if (!e0received) {
         table = (altPressed ? LeftAltScanCodes
                 : (controlPressed ? LeftControlScanCodes
@@ -65,7 +65,7 @@ static void KeybPrint(uchar _code)
     }
 
     uchar ch = KEY(code);
-    
+
     if (!ch) {
         switch (code) {
         case 0xE0: e0received = 1; break;
@@ -82,12 +82,12 @@ static void KeybPrint(uchar _code)
 
         case 0x1D: controlPressed = 1; break;
         case 0x9D: controlPressed = 0; break;
-        
+
         case 0x3A: capsLockActive = !capsLockActive; break;
         }
         return;
     }
-    
+
     bputc(BStdIn, ch);
 }
 
@@ -114,7 +114,7 @@ void IoCreateInputBuffer(void)
 
     rc = BOpenPureBuf(&BStdIn, BS_RDWR, 4 * KB);
 
-    if (rc) KeStartPanic("[Keyb] Couldn't create BStdIn");
+    if (rc < EOK) KeStartPanic("[Keyb] Couldn't create BStdIn");
 
     //BEnableLineBuffering(BStdIn);
     BStdIn->flusher = bemptybuf;
@@ -123,13 +123,13 @@ void IoCreateInputBuffer(void)
 void IoEnableKeyb(void)
 {
     ulong flags = KePauseIRQs();
- 
+
     KeRegisterISR(KeybHandler, 0x21);
     KeUnmaskIRQ(0x1);
     KeRestoreIRQs(flags);
 
     KeEnableNMI();
-    
+
     IoCreateInputBuffer();
 }
 
diff --git a/kaleid/kernel/mm/malloc.c b/kaleid/kernel/mm/malloc.c
index ab733b5..6f93669 100644
--- a/kaleid/kernel/mm/malloc.c
+++ b/kaleid/kernel/mm/malloc.c
@@ -45,7 +45,7 @@ error_t KalAllocMemoryEx(void **ptr, size_t req, int flags, size_t align)
 
     brk = (size_t)_heap_start + MmGetHeapSize();
     req = _ALIGN_UP(req + brk, align) - brk;
-    
+
     /* DebugLog("MALLOC: start=%p, size=%lx, brk=%p, req=%lx\n", */
     /*           _heap_start, MmGetHeapSize(), brk, req); */
 
@@ -53,7 +53,7 @@ error_t KalAllocMemoryEx(void **ptr, size_t req, int flags, size_t align)
 
     MmUnlockHeap();
 
-    if (rc) {
+    if (rc < EOK) {
         if ((flags & M_CANFAIL) != 0)
             return rc;
         KeStartPanic("KalAllocMemory: Out of memory");
diff --git a/kaleid/kernel/mm/map.c b/kaleid/kernel/mm/map.c
index e3448e1..7367149 100644
--- a/kaleid/kernel/mm/map.c
+++ b/kaleid/kernel/mm/map.c
@@ -41,7 +41,7 @@ void MmInitMemoryMap(void)
 
     rc = InitMemoryMap();
 
-    if (rc)
+    if (rc < EOK)
         KeStartPanic("Failed to initialize the memory map\nError : %s",
             strerror(rc) );
 }
diff --git a/kaleid/kernel/sh/shcmds.c b/kaleid/kernel/sh/shcmds.c
index b5b1e9f..406233d 100644
--- a/kaleid/kernel/sh/shcmds.c
+++ b/kaleid/kernel/sh/shcmds.c
@@ -120,7 +120,7 @@ error_t CmdDmesg(int argc, char **argv, char *cmdline)
 
     BLockBuf(BStdDbg);
 
-    ptr = (char *)lmax((ulong)BStdDbg->buf, 
+    ptr = (char *)lmax((ulong)BStdDbg->buf,
                (ulong)(BStdDbg->wp - BStdDbg->lastLF - (BStdDbg->lineLen * N)));
 
     KernLog(ptr);
diff --git a/kaleid/kernel/sh/shell.c b/kaleid/kernel/sh/shell.c
index c9eede8..b2c3d91 100644
--- a/kaleid/kernel/sh/shell.c
+++ b/kaleid/kernel/sh/shell.c
@@ -45,24 +45,28 @@ void ExecuteCommand(char *cmdbuf, Command_t *cmdtable)
     error_t rc;
     Command_t *cmd;
     bool found = false;
-    
+
     if (!cmdbuf || !*cmdbuf)
         return;
 
     memzero(*shargv, ARG_MAX);
     rc = ShCmdLineToArgVec(cmdbuf, &shargc, argvbuf);
-    if (rc) KeStartPanic("Shell: Couldn't parse command line: %d", rc);
+    if (rc < EOK) KeStartPanic("Shell: Couldn't parse command line: %d", rc);
 
     for (cmd = cmdtable; cmd->name != NULL; cmd++) {
         if (!strcmp(cmd->name, shargv[0])) {
-            cmd->func(shargc, shargv, cmdbuf);
+            rc = cmd->func(shargc, shargv, cmdbuf);
             found = true;
             break;
         }
     }
-    
+
+    if (found && rc < EOK) {
+        KernLog("\nerr: %s: return with error code %d: %s\n", cmd->name, rc, strerror(rc));
+    }
+
     assert(shargv[0] == argvbuf + ARG_MAX);
-    
+
     if (found == false) {
         KernLog("err: command not found: '%.255s' (%ld)\n",
                     shargv[0], strlen(shargv[0]));
@@ -88,9 +92,8 @@ void ShStartShell(void)
     char *history = malloc(CMDBUFSIZE * N);
     int historyIndex = 0;
     int historyScroll = 0;
-    
+
     bool insertMode = 0;
-    size_t nLines;
 
     argvbuf = malloc(ARG_MAX * 2);
     memzero(argvbuf, ARG_MAX * 2);
@@ -103,7 +106,7 @@ void ShStartShell(void)
     KernLog("\n%C%s%C", VGA_COLOR_WHITE, shprompt, shcol);
     BFlushBuf(BStdOut);
 
-    while ((rc = BGetFromBuf(BStdIn, &ch)) == EOK || rc == EENDF) {
+    while ((rc = BGetFromBuf(BStdIn, &ch)) >= EOK || rc == EENDF) {
         // Reset BStdIn's content
         if (rc == EENDF) {
             if (!(BStdIn->flags & BF_ERR)) {
@@ -118,7 +121,7 @@ void ShStartShell(void)
             }
             else break;
         }
-    
+
         switch (ch) {
 
         // Backspace character
@@ -145,22 +148,22 @@ void ShStartShell(void)
         case K_ESCAPE:      PoShutdown();   break;
         case K_PAGE_UP:     IoScrollUp();   break;
         case K_PAGE_DOWN:   IoScrollDown(); break;
-        
+
         case K_INSERT:
             insertMode = 1 - insertMode;
             break;
-    
+
         // Move within buffer
         case K_ARRW_LEFT:
             if (!(bufptr > cmdbuf))
                 break;
 
             bufptr--;
-            
+
             IoSetCursorOffset(IoGetCursorOffset()-1);
             BFlushBuf(BStdOut);
             break;
-    
+
         case K_ARRW_RIGHT:
             if (bufptr == bufend)
                 break;
@@ -169,7 +172,7 @@ void ShStartShell(void)
             IoSetCursorOffset(IoGetCursorOffset()+1);
             BFlushBuf(BStdOut);
             break;
-        
+
         case K_HOME:
             if (bufptr == cmdbuf)
                 break;
@@ -178,7 +181,7 @@ void ShStartShell(void)
             bufptr = cmdbuf;
             BFlushBuf(BStdOut);
             break;
-            
+
         case K_END:
             if (bufptr == bufend)
                 break;
@@ -221,7 +224,7 @@ void ShStartShell(void)
 
                 bufend = bufptr;
                 *bufptr = 0;
-                
+
                 // Advance cursor
                 if (IoGetCursorOffset() < 0)
                     IoSetCursorOffset(IoGetCursorOffset() + 1);
@@ -254,7 +257,7 @@ void ShStartShell(void)
                 VGA_COLOR_WHITE, shprompt, shcol, cmdbuf);
 
             BUnlockBuf(BStdOut);
-            
+
             IoSetScroll(1);
             IoScrollDown();     // This calls the flusher
 
@@ -283,13 +286,13 @@ void ShStartShell(void)
                     assert(historyIndex == N);
                     memmove(history, history+CMDBUFSIZE, CMDBUFSIZE * (N-1));
                     historyIndex = historyScroll = N-1;
-                    
+
                 }
                 // Update history
                 memmove(&history[historyIndex*CMDBUFSIZE], cmdbuf, CMDBUFSIZE);
                 historyScroll = historyIndex;
                 historyIndex++;
-                
+
                 // Execute & reset
                 ExecuteCommand(cmdbuf, shcmdtable);
                 memzero(cmdbuf, CMDBUFSIZE);
diff --git a/kaleid/libbuf/bgetc.c b/kaleid/libbuf/bgetc.c
index 9b1c009..fd45ae1 100644
--- a/kaleid/libbuf/bgetc.c
+++ b/kaleid/libbuf/bgetc.c
@@ -51,9 +51,9 @@ error_t bgetc(Buffer_t *buf, uchar *ch)
     error_t rc = EOK;
 
     if (buf->flags & (BF_EOF|BF_ERR)) return EENDF;
-    
+
     assert(!(buf->rp > buf->wp)); // Shouldn't be possible right now
-    
+
     if (buf->rp == buf->buf + buf->size) {
         buf->flags |= BF_EOF;
         return EENDF;
@@ -64,7 +64,7 @@ error_t bgetc(Buffer_t *buf, uchar *ch)
         *ch = *buf->rp++;
         return EOK;
     }
-    
+
     // We need to fill the buffer
     else {
         // We need a BFiller_t
@@ -78,14 +78,14 @@ error_t bgetc(Buffer_t *buf, uchar *ch)
             return EENDF;   // Currently empty
 #endif
         }
-        
+
         *ch = *buf->rp++;
     }
-    
-    if (rc != EOK) {
+
+    if (rc < EOK) {
         // buf->flags |= BF_ERR;
     }
-    
+
     return rc;
 }
 
diff --git a/kaleid/libbuf/bopen.c b/kaleid/libbuf/bopen.c
index a97d660..e609a86 100644
--- a/kaleid/libbuf/bopen.c
+++ b/kaleid/libbuf/bopen.c
@@ -76,13 +76,13 @@ error_t BOpenPureBufEx(Buffer_t **pbuf, char *source, int mode, size_t size,
     buf->flusher = flusher;
 
     ExReleaseLock(&buf->lock);
-    
+
     // Second allocation failed
     if (buf->buf == NULL) {
         BCloseBuf(buf);
         return ENOMEM;
     }
-    
+
     *pbuf = buf;
     return EOK;
 }
@@ -108,16 +108,16 @@ error_t BOpenTermBufEx(Buffer_t **pbuf, char *source, int mode,
     size_t size = lineLen * nLines * (pbCount + 1);
 
     assert(lineLen > 0 && nLines > 0 && pbCount >= 0);
-    
+
     rc = BOpenPureBufEx(pbuf, source, mode, size, flusher);
-    
-    if (!rc) {
+
+    if (!(rc < 0)) {
         (*pbuf)->lastLF = 0;
         (*pbuf)->nLines = nLines;
         (*pbuf)->lineLen = lineLen;
         (*pbuf)->flags |= BF_TERM;
     }
-     
+
     return rc;
 }
 
diff --git a/kaleid/libbuf/bprint.c b/kaleid/libbuf/bprint.c
index bfa6b51..bb4e9b7 100644
--- a/kaleid/libbuf/bprint.c
+++ b/kaleid/libbuf/bprint.c
@@ -48,11 +48,11 @@ size_t BPrintOnBuf(Buffer_t *buf, const char *fmt, ...)
 size_t BPrintOnBufV(Buffer_t *buf, const char *fmt, va_list ap)
 {
     size_t sz;
-    
+
     ExAcquireLock(&buf->lock);
     sz = vbprintf(buf, fmt, ap);
     ExReleaseLock(&buf->lock);
-    
+
     return sz;
 }
 
@@ -111,7 +111,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
     }
 
     // Progress in format string
-    while (*fmt && !rc) {
+    while (*fmt && !(rc < EOK)) {
 
         // Deal with all non-'%' characters
         if (*fmt != '%') {
@@ -149,7 +149,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
             else if (*fmt == '+') { fmt++; plus++; }
             else if (*fmt == '-') { fmt++; minus++; }
             else if (*fmt == ' ') { fmt++; space++; }
-            
+
             // Next field
             else break;
         }
@@ -172,7 +172,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
                 }                                                       \
             }                                                           \
         } while (0)
-        
+
         // Extract width
         bextractwp(width);
 
@@ -181,7 +181,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
             width = -width;
             minus++;
         }
-        
+
         // Extract precision
         if (*fmt == '.') {
             fmt++;
@@ -202,7 +202,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
                 fmt++;
                 h++;
             }
-            
+
             // Next field
             else break;
         }
@@ -228,7 +228,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
 #ifdef _KALEID_KERNEL
         if (type == 'C') {
             base = va_arg(ap, int);
-            
+
             if (!(base < 0 || base > VGA_COLOR_WHITE)) {
                 rc = bputc(buf, RtlColorToChar(base));
                 written++;
@@ -248,18 +248,18 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
             // amount of characters to be read from the stream
             // Zero/nonspecified precision means unlimited amount
             if (prec == 0) prec = INT_MAX;
-            
-            for (; !rc && *s && prec-- ; s++) {
+
+            for (; !(rc < EOK) && *s && prec-- ; s++) {
                 rc = bputc(buf, (uchar)*s);
                 written++;
             }
 
             continue;
         }
-        
+
 
         // Make sure width and prec aren't too big
-        // (We didn't do that earlier because %s uses width) 
+        // (We didn't do that earlier because %s uses width)
         if (width > CONVBUFSIZE || prec > CONVBUFSIZE) {
             written++; // Work around "if (rc) return written - 1;"
             rc = EINVAL;
@@ -339,7 +339,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
             // Reset s
             s = convbuf;
         }
-        
+
         // Compute s's length
         // It will always fit in an int
         else len = (int)strlen(s);
@@ -353,7 +353,7 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
 
         // When padding with spaces, we pad before +/-'s etc
         if (!minus && !zero && width > len) {
-            for (; !rc && width > len ; width--) {
+            for (; !(rc < EOK) && width > len ; width--) {
                 rc = bputc(buf, ' ');
                 written++;
             }
@@ -365,11 +365,11 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
         else if (sgn && space) { rc = bputc(buf, ' '); written++; }
 
         // Print 0 for octal, 0x for hexadecimal, 0b for binary
-        else if (hash && (base == 2 || base == 8 || base == 16)) { 
+        else if (hash && (base == 2 || base == 8 || base == 16)) {
             rc = bputc(buf, '0');
             written++;
 
-            if (!rc && base != 8) {
+            if (!(rc < EOK) && base != 8) {
                 rc = bputc(buf, (base == 2 ? 'b' : (cap ? 'X' : 'x')));
                 written++;
             }
@@ -378,34 +378,34 @@ size_t vbprintf(Buffer_t *buf, const char *fmt, va_list ap)
         // Deal with padding by zeroes
         // The 'minus' flag makes no sense with the 'zero' one
         if (zero && width > len) {
-            for (; !rc && width > len ; width--) {
+            for (; !(rc < EOK) && width > len ; width--) {
                 rc = bputc(buf, '0');
                 written++;
             }
         }
 
         // Output the actual number
-        for (; !rc && *s ; s++) {
+        for (; !(rc < EOK) && *s ; s++) {
             rc = bputc(buf, (uchar)*s);
             written++;
         }
 
         // 'minus' padding, only with spaces
         if (minus && !zero && width > len) {
-            for (; !rc && width > len ; width--) {
+            for (; !(rc < EOK) && width > len ; width--) {
                 rc = bputc(buf, ' ');
                 written++;
             }
         }
-            
+
         // Carry on to next modifier
     }
 
     // For debugging purposes
-    assert(!rc && "vbprintf() error");
+    assert(!(rc < EOK) && "vbprintf() error");
     seterrno(rc);
 
-    if (rc)
+    if (rc < EOK)
         return written - 1;     // "- 1" because last bputc() must have failed
     else
         return written;
diff --git a/kaleid/libbuf/bputc.c b/kaleid/libbuf/bputc.c
index 58c1935..ec6a43d 100644
--- a/kaleid/libbuf/bputc.c
+++ b/kaleid/libbuf/bputc.c
@@ -60,7 +60,7 @@ error_t bputc(Buffer_t *buf, uchar ch)
         // We need a field for choosing a different filler, e.g. '\0'
         if (ch == '\n') {
             assert(buf->lastLF < buf->lineLen);
-            
+
             int off = buf->lineLen - buf->lastLF;
             while (off > 0) {
                 *buf->wp++ = ' ';
@@ -124,23 +124,23 @@ error_t bputc(Buffer_t *buf, uchar ch)
         }
 
         *buf->wp++ = ch;
-        
+
         if (buf->wp == buf->buf + buf->size) {
             if (!(buf->flags & (BF_LINE|BF_FONCLOSE))) {
                 if (buf->flusher) buf->flusher(buf);
             }
         }
-        
+
         // Line-buffering
         if (ch == '\n' && buf->flags & BF_LINE) {
             if (buf->flusher) buf->flusher(buf);
         }
     }
-    
-    if (rc != EOK) {
+
+    if (rc < EOK) {
         // buf->flags |= BF_ERR;
     }
-    
+
     return rc;
 }
 
diff --git a/kaleid/libbuf/bscan.c b/kaleid/libbuf/bscan.c
index 5e12f97..3366988 100644
--- a/kaleid/libbuf/bscan.c
+++ b/kaleid/libbuf/bscan.c
@@ -45,11 +45,11 @@ size_t BScanFromBuf(Buffer_t *buf, const char *fmt, ...)
 size_t BScanFromBufV(Buffer_t *buf, const char *fmt, va_list ap)
 {
     size_t rc;
-    
+
     ExAcquireLock(&buf->lock);
     sz = vbscanf(buf, fmt, ap);
     ExReleaseLock(&buf->lock);
-    
+
     return sz;
 }
 
@@ -85,15 +85,15 @@ size_t vbscanf(Buffer_t *buf, const char *fmt, va_list ap)
     }
 
     // Progress in format string
-    for (*fmt && !rc) {
-        
+    for (*fmt && !(rc < EOK)) {
+
         // Skip all kinds of whitespaces
         if (isspace(*fmt)) {
 
         another_space:
             rc = bgetc(buf, &ch);
 
-            if (!rc) break;
+            if (!(rc < EOK)) break;
 
             // Put back non-whitespaces and progress
             if (!isspace(ch)) {
@@ -104,13 +104,13 @@ size_t vbscanf(Buffer_t *buf, const char *fmt, va_list ap)
 
             else goto another_space;
         }
-    
+
         // Deal with all non-'%' non-whitespace characters
         if (*fmt != '%') {
             rc = bgetc(buf, &ch);
 
             // Is it what we expected?
-            if (!rc && ch != *fmt) {
+            if (!(rc < EOK) && ch != *fmt) {
                 // No, so put it back
                 buf->rp--;
                 break;
@@ -131,11 +131,11 @@ size_t vbscanf(Buffer_t *buf, const char *fmt, va_list ap)
         if (*fmt == '%') {
             rc = bgetc(buf, &ch);
 
-            if (!rc && ch != '%') {
+            if (!(rc < EOK) && ch != '%') {
                 buf->rp--;
                 break;
             }
-            
+
             continue;
         }
 
@@ -155,7 +155,7 @@ size_t vbscanf(Buffer_t *buf, const char *fmt, va_list ap)
             fmt++;
         }
 
-        assert(!(width < 0)); 
+        assert(!(width < 0));
 
         //
         // Extract length field
@@ -180,10 +180,10 @@ size_t vbscanf(Buffer_t *buf, const char *fmt, va_list ap)
             if (width == 0) width = 1;
 
             // For >1 width, read that many characters
-            // then store them in successive argument pointers 
+            // then store them in successive argument pointers
             for (; width; width--) {
                 rc = bgetc(buf, &ch);
-                if (!rc) break;
+                if (!(rc < EOK)) break;
 
                 char *chptr = va_arg(ap, char *);
                  *chptr = (char)ch;
@@ -193,12 +193,12 @@ size_t vbscanf(Buffer_t *buf, const char *fmt, va_list ap)
 
         // Decimal integer
         else if (*fmt == 'd') {
-            
+
         }
     }
 
     // For debugging purposes
-    assert(!rc && "vbscanf() error");
+    assert(!(rc < EOK) && "vbscanf() error");
     seterrno(rc);
 
     return readcnt;
@@ -208,4 +208,3 @@ size_t vbscanf(Buffer_t *buf, const char *fmt, va_list ap)
 
 #endif
 
-
diff --git a/kaleid/libc/errno.c b/kaleid/libc/errno.c
index 4abdca7..c0d25ff 100644
--- a/kaleid/libc/errno.c
+++ b/kaleid/libc/errno.c
@@ -25,11 +25,11 @@
 #include <libc.h>
 #undef _ERRNO_H
 
-#define _estart
-#define _eentry(code, desc)     [code] = desc,
-#define _eend
+#define _ESTART
+#define _EENTRY(code, num, desc)     [-code] = desc,
+#define _EEND
 
-char *__strerror[_EMAX] = {
+char *__strerror[] = {
 
 #include <errno.h>
 
@@ -37,6 +37,9 @@ char *__strerror[_EMAX] = {
 
 const char *strerror(error_t code)
 {
-    return __strerror[code];
+    if (code > 0 || code <= _EMAX)
+        return NULL;
+
+    return __strerror[-code];
 }
 
diff --git a/kaleid/libc/mem.c b/kaleid/libc/mem.c
index feb7624..fac8b2e 100644
--- a/kaleid/libc/mem.c
+++ b/kaleid/libc/mem.c
@@ -41,7 +41,7 @@ void *malloc(size_t n)
 #else
     rc = KalAllocMemoryEx(&ptr, n, M_ZEROED, 0);
 #endif
-    if (rc > 0) seterrno(rc);
+    if (rc < EOK) seterrno(rc);
 
     return ptr;
 }
@@ -56,7 +56,7 @@ void *memalign(size_t n, size_t align)
 #else
     rc = KalAllocMemoryEx(&ptr, n, M_ZEROED, align);
 #endif
-    if (rc > 0) seterrno(rc);
+    if (rc < EOK) seterrno(rc);
 
     return ptr;
 }
@@ -65,10 +65,10 @@ void *calloc(size_t n, size_t m)
 {
     void *ptr;
     error_t rc;
-    
+
     rc = KalAllocMemoryEx(&ptr, n * m, M_ZEROED, 0);
-    if (rc > 0) seterrno(rc);
-    
+    if (rc < EOK) seterrno(rc);
+
     return ptr;
 }
 
diff --git a/kaleid/libc/sprintf.c b/kaleid/libc/sprintf.c
index d1f3dcc..5d26348 100644
--- a/kaleid/libc/sprintf.c
+++ b/kaleid/libc/sprintf.c
@@ -92,7 +92,7 @@ size_t vsnprintf(char *str, size_t n, const char *fmt, va_list ap)
     rc = BOpenPureBuf(&buf, BS_WRONLY, n-1);
 
     // n-1 to leave place for the '\0'
-    if (rc != EOK) {
+    if (rc < EOK) {
         goto fail;
     }
 
@@ -101,9 +101,9 @@ size_t vsnprintf(char *str, size_t n, const char *fmt, va_list ap)
     // We don't mind EOFs, just just return how much was successfully written
     if (sz == 0 && !(buf->flags & BF_EOF))
             goto fail;
-    
+
     ret = (size_t)buf->wp - (size_t)buf->buf;
-    
+
     if (ret > 0)
         memmove(str, (char *)buf->buf, ret);