diff --git a/src/debug.c b/src/debug.c
index d14c998..f56a944 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -18,12 +18,16 @@
 
 #include "config.h"
 
+/* Do we want our debug() call to be safe wrt. signals? */
+#define SAFE_FUNCTION
+
 #if defined HAVE_STDINT_H
 #   include <stdint.h>
 #elif defined HAVE_INTTYPES_H
 #   include <inttypes.h>
 #endif
 #include <stdio.h>
+#include <unistd.h>
 #include <errno.h>
 #include <stdarg.h>
 
@@ -31,19 +35,104 @@
 
 extern int _zz_hasdebug;
 
-void _zz_debug(const char *format, ...)
+#define WRITE_INT(fd, i, base) \
+    char buf[128], *b = buf + 127; \
+    if(i <= 0) \
+        write(fd, (i = -i) ? "-" : "0", 1); /* XXX: hack here */ \
+    while(i) \
+    { \
+        *b-- = hex2char[i % base]; \
+        i /= base; \
+    } \
+    write(fd, b + 1, buf + 127 - b)
+
+void _zz_debug(char const *format, ...)
 {
+#ifdef SAFE_FUNCTION
+    static char const *hex2char = "0123456789abcdef";
+    char const *f;
+#endif
     va_list args;
-    int saved_errno;
+    int saved_errno, fd = 2;
 
     if(!_zz_hasdebug)
         return;
 
     saved_errno = errno;
     va_start(args, format);
+#ifdef SAFE_FUNCTION
+    write(fd, "** zzuf debug ** ", 17);
+    for(f = format; *f; f++)
+    {
+        if(*f != '%')
+        {
+            write(fd, f, 1);
+            continue;
+        }
+
+        f++;
+        if(!*f)
+            break;
+
+        if(*f == 'i')
+        {
+            int i = va_arg(args, int);
+            WRITE_INT(fd, i, 10);
+        }
+        else if(f[0] == 'l' && f[1] == 'i')
+        {
+            long int i = va_arg(args, long int);
+            WRITE_INT(fd, i, 10);
+            f++;
+        }
+        else if(f[0] == 'l' && f[1] == 'l' && f[2] == 'i')
+        {
+            long long int i = va_arg(args, long long int);
+            WRITE_INT(fd, i, 10);
+            f += 2;
+        }
+        else if(f[0] == 'p')
+        {
+            uintptr_t i = va_arg(args, uintptr_t);
+            if(!i)
+                write(fd, "(nil)", 5);
+            else
+            {
+                write(fd, "0x", 2);
+                WRITE_INT(fd, i, 16);
+            }
+        }
+        else if(f[0] == 's')
+        {
+            char *s = va_arg(args, char *);
+            if(!s)
+                write(fd, "(nil)", 5);
+            else
+            {
+                int l = 0;
+                while(s[l])
+                    l++;
+                write(fd, s, l);
+            }
+        }
+        else if(f[0] == '0' && f[1] == '2' && f[2] == 'x')
+        {
+            int i = va_arg(args, int);
+            write(fd, hex2char + ((i & 0xf0) >> 4), 1);
+            write(fd, hex2char + (i & 0x0f), 1);
+            f += 2;
+        }
+        else
+        {
+            write(fd, f, 1);
+        }
+    }
+    write(fd, "\n", 1);
+#else
     fprintf(stderr, "** zzuf debug ** ");
     vfprintf(stderr, format, args);
     fprintf(stderr, "\n");
+#endif
     va_end(args);
     errno = saved_errno;
 }