diff --git a/caca/caca.c b/caca/caca.c
index 3c96901..d437dda 100644
--- a/caca/caca.c
+++ b/caca/caca.c
@@ -24,9 +24,6 @@
 #   include <stdlib.h>
 #   include <string.h>
 #   include <stdio.h>
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #   if defined(USE_PLUGINS)
 #       if defined(HAVE_DLFCN_H)
 #           include <dlfcn.h>
@@ -69,9 +66,7 @@ caca_display_t * caca_create_display(cucul_canvas_t * cv)
 
     if(!dp)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = ENOMEM;
-#endif
+        seterrno(ENOMEM);
         return NULL;
     }
 
@@ -87,9 +82,7 @@ caca_display_t * caca_create_display(cucul_canvas_t * cv)
             dlclose(dp->plugin);
 #endif
         free(dp);
-#if defined(HAVE_ERRNO_H)
-        errno = ENODEV;
-#endif
+        seterrno(ENODEV);
         return NULL;
     }
 
@@ -100,9 +93,7 @@ caca_display_t * caca_create_display(cucul_canvas_t * cv)
             dlclose(dp->plugin);
 #endif
         free(dp);
-#if defined(HAVE_ERRNO_H)
-        errno = ENODEV;
-#endif
+        seterrno(ENODEV);
         return NULL;
     }
 
diff --git a/caca/graphics.c b/caca/graphics.c
index 641bcf2..7dc304d 100644
--- a/caca/graphics.c
+++ b/caca/graphics.c
@@ -18,12 +18,6 @@
 #include "config.h"
 #include "common.h"
 
-#if !defined(__KERNEL__)
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
-#endif
-
 #include "caca.h"
 #include "caca_internals.h"
 #include "cucul.h"
@@ -45,10 +39,8 @@ int caca_set_display_title(caca_display_t *dp, char const *title)
 {
     int ret = dp->drv.set_display_title(dp, title);
 
-#if defined(HAVE_ERRNO_H)
     if(ret)
-        errno = ENOSYS;
-#endif
+        seterrno(ENOSYS);
 
     return ret;
 }
@@ -195,9 +187,7 @@ int caca_set_mouse(caca_display_t *dp, int flag)
 {
     if(!dp->drv.set_mouse)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = ENOSYS;
-#endif
+        seterrno(ENOSYS);
         return -1;
     }
 
diff --git a/common.h b/common.h
index daef8d4..84d817c 100644
--- a/common.h
+++ b/common.h
@@ -17,6 +17,7 @@
  *  function prototypes that are sometimes missing.
  */
 
+/* C99 types */
 #if defined HAVE_INTTYPES_H && !defined __KERNEL__
 #   include <inttypes.h>
 #else
@@ -32,31 +33,36 @@ typedef long int intptr_t;
 typedef unsigned long int uintptr_t;
 #endif
 
+/* errno handling */
+#if defined HAVE_ERRNO_H && !defined __KERNEL__
+#   include <errno.h>
+static inline void seterrno(int e) { errno = e; }
+static inline int geterrno(void) { return errno; }
+#else
+#   define seterrno(x) do {} while(0)
+#   define geterrno(x) 0
+#endif
+
+/* debug messages */
 #if defined DEBUG && !defined __KERNEL__
 #   include <stdio.h>
 #   include <stdarg.h>
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 static inline void debug(const char *format, ...)
 {
-#   if defined(HAVE_ERRNO_H)
-    int saved_errno = errno;
-#   endif
+    int saved_errno = geterrno();
     va_list args;
     va_start(args, format);
     fprintf(stderr, "** libcaca debug ** ");
     vfprintf(stderr, format, args);
     fprintf(stderr, "\n");
     va_end(args);
-#   if defined(HAVE_ERRNO_H)
-    errno = saved_errno;
-#   endif
+    seterrno(saved_errno);
 }
 #else
 #   define debug(format, ...) do {} while(0)
 #endif
 
+/* hton16() and hton32() */
 #if defined HAVE_HTONS
 #   if defined __KERNEL__
         /* Nothing to do */
@@ -101,7 +107,3 @@ static inline uint32_t hton32(uint32_t x)
 }
 #endif
 
-#if defined __KERNEL__
-#   undef HAVE_ERRNO_H
-#endif
-
diff --git a/cucul/attr.c b/cucul/attr.c
index 4648173..22a03a0 100644
--- a/cucul/attr.c
+++ b/cucul/attr.c
@@ -19,10 +19,6 @@
 #include "config.h"
 #include "common.h"
 
-#if defined(HAVE_ERRNO_H)
-#   include <errno.h>
-#endif
-
 #include "cucul.h"
 #include "cucul_internals.h"
 
@@ -89,9 +85,7 @@ int cucul_set_attr(cucul_canvas_t *cv, unsigned long int attr)
 {
     if(sizeof(unsigned long int) > sizeof(uint32_t) && attr > 0xffffffff)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -131,9 +125,7 @@ int cucul_put_attr(cucul_canvas_t *cv, int x, int y, unsigned long int attr)
 
     if(sizeof(unsigned long int) > sizeof(uint32_t) && attr > 0xffffffff)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -177,9 +169,7 @@ int cucul_set_color_ansi(cucul_canvas_t *cv, unsigned char fg, unsigned char bg)
 
     if(fg > 0x20 || bg > 0x20)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -213,9 +203,7 @@ int cucul_set_color_argb(cucul_canvas_t *cv, unsigned int fg, unsigned int bg)
 
     if(fg > 0xffff || bg > 0xffff)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
diff --git a/cucul/canvas.c b/cucul/canvas.c
index 8400b3e..40a9b7e 100644
--- a/cucul/canvas.c
+++ b/cucul/canvas.c
@@ -24,9 +24,6 @@
 #   include <string.h>
 #   include <stdlib.h>
 #   include <stdarg.h>
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #   if defined(HAVE_UNISTD_H)
 #       include <unistd.h>
 #   endif
@@ -384,9 +381,7 @@ int cucul_blit(cucul_canvas_t *dst, int x, int y,
 
     if(mask && (src->width != mask->width || src->height != mask->height))
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -471,9 +466,7 @@ int cucul_set_canvas_boundaries(cucul_canvas_t *cv, int x, int y,
 
     if(cv->refcount)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EBUSY;
-#endif
+        seterrno(EBUSY);
         return -1;
     }
 
diff --git a/cucul/cucul.c b/cucul/cucul.c
index b552231..8894e4c 100644
--- a/cucul/cucul.c
+++ b/cucul/cucul.c
@@ -24,9 +24,6 @@
 #   include <stdlib.h>
 #   include <string.h>
 #   include <time.h>
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #   include <sys/types.h>
 #   if defined(HAVE_UNISTD_H)
 #       include <unistd.h>
@@ -87,23 +84,17 @@ cucul_canvas_t * cucul_create_canvas(unsigned int width, unsigned int height)
 
     if(_cucul_set_canvas_size(cv, width, height) < 0)
     {
-#if defined(HAVE_ERRNO_H)
-        int saved_errno = errno;
-#endif
+        int saved_errno = geterrno();
         free(cv->frames);
         free(cv);
-#if defined(HAVE_ERRNO_H)
-        errno = saved_errno;
-#endif
+        seterrno(saved_errno);
         return NULL;
     }
 
     return cv;
 
 nomem:
-#if defined(HAVE_ERRNO_H)
-    errno = ENOMEM;
-#endif
+    seterrno(ENOMEM);
     return NULL;
 }
 
@@ -137,9 +128,7 @@ int cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
 {
     if(cv->refcount)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EBUSY;
-#endif
+        seterrno(EBUSY);
         return -1;
     }
 
@@ -192,9 +181,7 @@ int cucul_free_canvas(cucul_canvas_t *cv)
 
     if(cv->refcount)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EBUSY;
-#endif
+        seterrno(EBUSY);
         return -1;
     }
 
@@ -262,9 +249,7 @@ int _cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
                                           new_size * sizeof(uint32_t));
             if(new_size && (!cv->frames[f].chars || !cv->frames[f].attrs))
             {
-#if defined(HAVE_ERRNO_H)
-                errno = ENOMEM;
-#endif
+                seterrno(ENOMEM);
                 return -1;
             }
         }
@@ -356,9 +341,7 @@ int _cucul_set_canvas_size(cucul_canvas_t *cv, unsigned int width,
                                           new_size * sizeof(uint32_t));
             if(new_size && (!cv->frames[f].chars || !cv->frames[f].attrs))
             {
-#if defined(HAVE_ERRNO_H)
-                errno = ENOMEM;
-#endif
+                seterrno(ENOMEM);
                 return -1;
             }
         }
diff --git a/cucul/dither.c b/cucul/dither.c
index 71055f6..73756d1 100644
--- a/cucul/dither.c
+++ b/cucul/dither.c
@@ -26,9 +26,6 @@
 #   include <stdlib.h>
 #   include <limits.h>
 #   include <string.h>
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #endif
 
 #include "cucul.h"
@@ -271,18 +268,14 @@ cucul_dither_t *cucul_create_dither(unsigned int bpp, unsigned int w,
     /* Minor sanity test */
     if(!w || !h || !pitch || bpp > 32 || bpp < 8)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return NULL;
     }
 
     d = malloc(sizeof(cucul_dither_t));
     if(!d)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = ENOMEM;
-#endif
+        seterrno(ENOMEM);
         return NULL;
     }
 
@@ -377,9 +370,7 @@ int cucul_set_dither_palette(cucul_dither_t *d,
 
     if(d->bpp != 8)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -387,9 +378,7 @@ int cucul_set_dither_palette(cucul_dither_t *d,
     {
         if((red[i] | green[i] | blue[i] | alpha[i]) >= 0x1000)
         {
-#if defined(HAVE_ERRNO_H)
-            errno = EINVAL;
-#endif
+            seterrno(EINVAL);
             return -1;
         }
     }
@@ -448,9 +437,7 @@ int cucul_set_dither_gamma(cucul_dither_t *d, float gamma)
 
     if(gamma <= 0.0)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -520,9 +507,7 @@ int cucul_set_dither_antialias(cucul_dither_t *d, char const *str)
         d->antialias = 1;
     else
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -596,9 +581,7 @@ int cucul_set_dither_color(cucul_dither_t *d, char const *str)
         d->color_mode = COLOR_MODE_FULL16;
     else
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -675,9 +658,7 @@ int cucul_set_dither_charset(cucul_dither_t *d, char const *str)
     }
     else
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -770,9 +751,7 @@ int cucul_set_dither_mode(cucul_dither_t *d, char const *str)
     }
     else
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
diff --git a/cucul/export.c b/cucul/export.c
index dbf1a9b..ded5a67 100644
--- a/cucul/export.c
+++ b/cucul/export.c
@@ -20,9 +20,6 @@
 #include "common.h"
 
 #if !defined(__KERNEL__)
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #   include <stdlib.h>
 #   include <stdio.h>
 #   include <string.h>
@@ -117,9 +114,7 @@ void *cucul_export_memory(cucul_canvas_t *cv, char const *format,
     if(!strcasecmp("tga", format))
         return export_tga(cv, bytes);
 
-#if defined(HAVE_ERRNO_H)
-    errno = EINVAL;
-#endif
+    seterrno(EINVAL);
     return NULL;
 }
 
@@ -276,8 +271,8 @@ static void *export_utf8(cucul_canvas_t *cv, unsigned long int *bytes, int cr)
     }
 
     /* Crop to really used size */
-    debug("utf8 export: alloc %li bytes, realloc %li\n",
-          (long int)*bytes, (long int)(uintptr_t)(cur - data));
+    debug("utf8 export: alloc %lu bytes, realloc %lu",
+          (unsigned long int)*bytes, (unsigned long int)(cur - data));
     *bytes = (uintptr_t)(cur - data);
     data = realloc(data, *bytes);
 
@@ -356,8 +351,8 @@ static void *export_ansi(cucul_canvas_t *cv, unsigned long int *bytes)
     }
 
     /* Crop to really used size */
-    debug("ansi export: alloc %li bytes, realloc %li\n",
-          (long int)*bytes, (long int)(uintptr_t)(cur - data));
+    debug("ansi export: alloc %lu bytes, realloc %lu",
+          (unsigned long int)*bytes, (unsigned long int)(cur - data));
     *bytes = (uintptr_t)(cur - data);
     data = realloc(data, *bytes);
 
@@ -432,8 +427,8 @@ static void *export_html(cucul_canvas_t *cv, unsigned long int *bytes)
     cur += sprintf(cur, "</div></body></html>\n");
 
     /* Crop to really used size */
-    debug("html export: alloc %li bytes, realloc %li\n",
-          (long int)*bytes, (long int)(uintptr_t)(cur - data));
+    debug("html export: alloc %lu bytes, realloc %lu",
+          (unsigned long int)*bytes, (unsigned long int)(cur - data));
     *bytes = (uintptr_t)(cur - data);
     data = realloc(data, *bytes);
 
@@ -527,8 +522,8 @@ static void *export_html3(cucul_canvas_t *cv, unsigned long int *bytes)
     cur += sprintf(cur, "</table>\n");
 
     /* Crop to really used size */
-    debug("html3 export: alloc %li bytes, realloc %li\n",
-          (long int)*bytes, (long int)(uintptr_t)(cur - data));
+    debug("html3 export: alloc %lu bytes, realloc %lu",
+          (unsigned long int)*bytes, (unsigned long int)(cur - data));
     *bytes = (uintptr_t)(cur - data);
     data = realloc(data, *bytes);
 
@@ -634,8 +629,8 @@ static void *export_irc(cucul_canvas_t *cv, unsigned long int *bytes)
     }
 
     /* Crop to really used size */
-    debug("IRC export: alloc %li bytes, realloc %li\n",
-          (long int)*bytes, (long int)(uintptr_t)(cur - data));
+    debug("IRC export: alloc %lu bytes, realloc %lu",
+          (unsigned long int)*bytes, (unsigned long int)(cur - data));
     *bytes = (uintptr_t)(cur - data);
     data = realloc(data, *bytes);
 
@@ -743,8 +738,8 @@ static void *export_ps(cucul_canvas_t *cv, unsigned long int *bytes)
     cur += sprintf(cur, "showpage\n");
 
     /* Crop to really used size */
-    debug("PS export: alloc %li bytes, realloc %li\n",
-          (long int)*bytes, (long int)(uintptr_t)(cur - data));
+    debug("PS export: alloc %lu bytes, realloc %lu",
+          (unsigned long int)*bytes, (unsigned long int)(cur - data));
     *bytes = (uintptr_t)(cur - data);
     data = realloc(data, *bytes);
 
@@ -829,8 +824,8 @@ static void *export_svg(cucul_canvas_t *cv, unsigned long int *bytes)
     cur += sprintf(cur, "</svg>\n");
 
     /* Crop to really used size */
-    debug("SVG export: alloc %li bytes, realloc %li\n",
-          (long int)*bytes, (long int)(uintptr_t)(cur - data));
+    debug("SVG export: alloc %lu bytes, realloc %lu",
+          (unsigned long int)*bytes, (unsigned long int)(cur - data));
     *bytes = (uintptr_t)(cur - data);
     data = realloc(data, *bytes);
 
@@ -848,9 +843,7 @@ static void *export_tga(cucul_canvas_t *cv, unsigned long int *bytes)
     fontlist = cucul_get_font_list();
     if(!fontlist[0])
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return NULL;
     }
 
diff --git a/cucul/font.c b/cucul/font.c
index e20f4ae..ba06d12 100644
--- a/cucul/font.c
+++ b/cucul/font.c
@@ -22,9 +22,6 @@
 #   if defined(HAVE_ENDIAN_H)
 #       include <endian.h>
 #   endif
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #   include <stdio.h>
 #   include <stdlib.h>
 #   include <string.h>
@@ -126,26 +123,22 @@ cucul_font_t *cucul_load_font(void const *data, unsigned int size)
         if(!strcasecmp(data, "Monospace Bold 12"))
             return cucul_load_font((char *)&monobold12_data, monobold12_size);
 
-#if defined(HAVE_ERRNO_H)
-        errno = ENOENT;
-#endif
+        seterrno(ENOENT);
         return NULL;
     }
 
     if(size < sizeof(struct font_header))
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        debug("font error: data size %i < header size %i",
+              size, (int)sizeof(struct font_header));
+        seterrno(EINVAL);
         return NULL;
     }
 
     f = malloc(sizeof(cucul_font_t));
     if(!f)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = ENOMEM;
-#endif
+        seterrno(ENOMEM);
         return NULL;
     }
 
@@ -167,10 +160,18 @@ cucul_font_t *cucul_load_font(void const *data, unsigned int size)
             f->header.bpp != 2 && f->header.bpp != 1)
         || (f->header.flags & 1) == 0)
     {
-        free(f);
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
+#if defined DEBUG
+        if(size != 4 + f->header.control_size + f->header.data_size)
+            debug("font error: data size %i < expected size %i",
+                  size, 4 + f->header.control_size + f->header.data_size);
+        else if(f->header.bpp != 8 && f->header.bpp != 4 &&
+                f->header.bpp != 2 && f->header.bpp != 1)
+            debug("font error: invalid bpp %i", f->header.bpp);
+        else if((f->header.flags & 1) == 0)
+            debug("font error: invalid flags %.04x", f->header.flags);
 #endif
+        free(f);
+        seterrno(EINVAL);
         return NULL;
     }
 
@@ -178,9 +179,7 @@ cucul_font_t *cucul_load_font(void const *data, unsigned int size)
     if(!f->block_list)
     {
         free(f);
-#if defined(HAVE_ERRNO_H)
-        errno = ENOMEM;
-#endif
+        seterrno(ENOMEM);
         return NULL;
     }
 
@@ -190,9 +189,7 @@ cucul_font_t *cucul_load_font(void const *data, unsigned int size)
     {
         free(f->block_list);
         free(f);
-#if defined(HAVE_ERRNO_H)
-        errno = ENOMEM;
-#endif
+        seterrno(ENOMEM);
         return NULL;
     }
 
@@ -209,12 +206,21 @@ cucul_font_t *cucul_load_font(void const *data, unsigned int size)
             || (i > 0 && f->block_list[i].start < f->block_list[i - 1].stop)
             || f->block_list[i].index >= f->header.glyphs)
         {
+#if defined DEBUG
+            if(f->block_list[i].start > f->block_list[i].stop)
+                debug("font error: block %i has start %i > stop %i",
+                      i, f->block_list[i].start, f->block_list[i].stop);
+            else if(i > 0 && f->block_list[i].start < f->block_list[i - 1].stop)
+                debug("font error: block %i has start %i < previous stop %i",
+                      f->block_list[i].start, f->block_list[i - 1].stop);
+            else if(f->block_list[i].index >= f->header.glyphs)
+                debug("font error: block %i has index >= glyph count %i",
+                      f->block_list[i].index, f->header.glyphs);
+#endif
             free(f->user_block_list);
             free(f->block_list);
             free(f);
-#if defined(HAVE_ERRNO_H)
-            errno = EINVAL;
-#endif
+            seterrno(EINVAL);
             return NULL;
         }
 
@@ -231,9 +237,7 @@ cucul_font_t *cucul_load_font(void const *data, unsigned int size)
         free(f->user_block_list);
         free(f->block_list);
         free(f);
-#if defined(HAVE_ERRNO_H)
-        errno = ENOMEM;
-#endif
+        seterrno(ENOMEM);
         return NULL;
     }
 
@@ -252,13 +256,24 @@ cucul_font_t *cucul_load_font(void const *data, unsigned int size)
                 + (f->glyph_list[i].width * f->glyph_list[i].height *
                    f->header.bpp + 7) / 8 > f->header.data_size)
         {
+#if defined DEBUG
+            if(f->glyph_list[i].data_offset >= f->header.data_size)
+                debug("font error: glyph %i has data start %i > "
+                      "data end %i",
+                      f->glyph_list[i].data_offset, f->header.data_size);
+            else if(f->glyph_list[i].data_offset
+                     + (f->glyph_list[i].width * f->glyph_list[i].height *
+                        f->header.bpp + 7) / 8 > f->header.data_size)
+                debug("font error: glyph %i has data end %i > "
+                      "data end %i", f->glyph_list[i].data_offset
+                       + (f->glyph_list[i].width * f->glyph_list[i].height *
+                          f->header.bpp + 7) / 8, f->header.data_size);
+#endif
             free(f->glyph_list);
             free(f->user_block_list);
             free(f->block_list);
             free(f);
-#if defined(HAVE_ERRNO_H)
-            errno = EINVAL;
-#endif
+            seterrno(EINVAL);
             return NULL;
         }
     }
diff --git a/cucul/frame.c b/cucul/frame.c
index 9372684..8ab5737 100644
--- a/cucul/frame.c
+++ b/cucul/frame.c
@@ -22,9 +22,6 @@
 #   include <stdio.h>
 #   include <stdlib.h>
 #   include <string.h>
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #endif
 
 #include "cucul.h"
@@ -66,9 +63,7 @@ int cucul_set_canvas_frame(cucul_canvas_t *cv, unsigned int frame)
 {
     if(frame >= cv->framecount)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
@@ -160,17 +155,13 @@ int cucul_free_canvas_frame(cucul_canvas_t *cv, unsigned int id)
 
     if(id >= cv->framecount)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
     if(cv->framecount == 1)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = EINVAL;
-#endif
+        seterrno(EINVAL);
         return -1;
     }
 
diff --git a/cucul/import.c b/cucul/import.c
index 417429d..96e0cb9 100644
--- a/cucul/import.c
+++ b/cucul/import.c
@@ -19,9 +19,6 @@
 #include "common.h"
 
 #if !defined __KERNEL__
-#   if defined HAVE_ERRNO_H
-#       include <errno.h>
-#   endif
 #   include <stdio.h>
 #   include <stdlib.h>
 #   include <string.h>
@@ -118,9 +115,7 @@ long int cucul_import_memory(cucul_canvas_t *cv, void const *data,
         return import_text(cv, data, len);
     }
 
-#if defined HAVE_ERRNO_H
-    errno = EINVAL;
-#endif
+    seterrno(EINVAL);
     return -1;
 }
 
@@ -157,9 +152,7 @@ long int cucul_import_file(cucul_canvas_t *cv, char const *filename,
                            char const *format)
 {
 #if defined __KERNEL__
-#   if defined HAVE_ERRNO_H
-    errno = ENOSYS;
-#   endif
+    seterrno(ENOSYS);
     return -1;
 #else
     FILE *fp;
@@ -178,9 +171,7 @@ long int cucul_import_file(cucul_canvas_t *cv, char const *filename,
     if(!data)
     {
         fclose(fp);
-#   if defined HAVE_ERRNO_H
-        errno = ENOMEM;
-#   endif
+        seterrno(ENOMEM);
         return -1;
     }
 
@@ -236,7 +227,10 @@ static long int import_caca(cucul_canvas_t *cv,
         return 0;
 
     if(buf[0] != 0xca || buf[1] != 0xca || buf[2] != 'C' || buf[3] != 'V')
+    {
+        debug("caca import error: expected \\xca\\xcaCV header");
         goto invalid_caca;
+    }
 
     control_size = sscanu32(buf + 4);
     data_size = sscanu32(buf + 8);
@@ -248,7 +242,11 @@ static long int import_caca(cucul_canvas_t *cv,
         return 0;
 
     if(control_size < 16 + frames * 32)
+    {
+        debug("caca import error: control size %lu < expected %lu",
+              (unsigned long int)control_size, 16 + frames * 32);
         goto invalid_caca;
+    }
 
     for(expected_size = 0, f = 0; f < frames; f++)
     {
@@ -269,7 +267,11 @@ static long int import_caca(cucul_canvas_t *cv,
     }
 
     if(expected_size != data_size)
+    {
+        debug("caca import error: data size %lu < expected %lu",
+              (unsigned long int)data_size, (unsigned long int)expected_size);
         goto invalid_caca;
+    }
 
     /* FIXME: read all frames, not only the first one */
     cucul_set_canvas_size(cv, 0, 0);
@@ -293,9 +295,7 @@ static long int import_caca(cucul_canvas_t *cv,
     return 4 + control_size + data_size;
 
 invalid_caca:
-#if defined HAVE_ERRNO_H
-    errno = EINVAL;
-#endif
+    seterrno(EINVAL);
     return -1;
 }
 
diff --git a/cucul/legacy.c b/cucul/legacy.c
index 4b8f1df..9e8ba6e 100644
--- a/cucul/legacy.c
+++ b/cucul/legacy.c
@@ -20,9 +20,6 @@
 #include "common.h"
 
 #if !defined(__KERNEL__)
-#   if defined(HAVE_ERRNO_H)
-#       include <errno.h>
-#   endif
 #   include <stdio.h>
 #   include <stdlib.h>
 #   include <string.h>
@@ -88,9 +85,7 @@ cucul_buffer_t * cucul_export_canvas(cucul_canvas_t *cv, char const *format)
     ex = malloc(sizeof(cucul_buffer_t));
     if(!ex)
     {
-#if defined(HAVE_ERRNO_H)
-        errno = ENOMEM;
-#endif
+        seterrno(ENOMEM);
         return NULL;
     }