diff --git a/labels.c b/labels.c
index 8c850c30..9152552e 100644
--- a/labels.c
+++ b/labels.c
@@ -224,7 +224,7 @@ void redefine_label(char *label, int32_t segment, int64_t offset, char *special,
 #if DEBUG<3
     if (!strncmp(label, "debugdump", 9))
 #endif
-        nasm_error(ERR_DEBUG, "redefine_label (%s, %ld, %08lx, %s, %d, %d)",
+        nasm_error(ERR_DEBUG, "redefine_label (%s, %"PRIx32", %"PRIx64", %s, %d, %d)",
               label, segment, offset, special, is_norm, isextrn);
 #endif
 
@@ -288,7 +288,7 @@ void define_label(char *label, int32_t segment, int64_t offset, char *special,
 #if DEBUG<3
     if (!strncmp(label, "debugdump", 9))
 #endif
-        nasm_error(ERR_DEBUG, "define_label (%s, %ld, %08lx, %s, %d, %d)",
+        nasm_error(ERR_DEBUG, "define_label (%s, %"PRIx32", %"PRIx64", %s, %d, %d)",
               label, segment, offset, special, is_norm, isextrn);
 #endif
     lptr = find_label(label, 1);
diff --git a/nasmlib.h b/nasmlib.h
index 3cb15bae..c42c3fd2 100644
--- a/nasmlib.h
+++ b/nasmlib.h
@@ -84,7 +84,11 @@ extern unsigned char nasm_tolower_tab[256];
  */
 typedef void (*efunc) (int severity, const char *fmt, ...);
 typedef void (*vefunc) (int severity, const char *fmt, va_list ap);
+#ifdef __GNUC__
+void nasm_error(int severity, const char *fmt, ...) __attribute__((format(printf, 2, 3)));
+#else
 void nasm_error(int severity, const char *fmt, ...);
+#endif
 void nasm_set_verror(vefunc);
 
 /*
diff --git a/output/outbin.c b/output/outbin.c
index 89c8ecf9..ba9947d9 100644
--- a/output/outbin.c
+++ b/output/outbin.c
@@ -241,7 +241,7 @@ static void bin_cleanup(int debuginfo)
     (void)debuginfo;      /* placate optimizers */
 
 #ifdef DEBUG
-    fprintf(stdout,
+    nasm_error(ERR_DEBUG,
             "bin_cleanup: Sections were initially referenced in this order:\n");
     for (h = 0, s = sections; s; h++, s = s->next)
         fprintf(stdout, "%i. %s\n", h, s->name);
@@ -530,7 +530,7 @@ static void bin_cleanup(int debuginfo)
         nasm_error(ERR_FATAL|ERR_NOFILE, "circular vfollows path detected");
 
 #ifdef DEBUG
-    fprintf(stdout,
+    nasm_error(ERR_DEBUG,
             "bin_cleanup: Confirm final section order for output file:\n");
     for (h = 0, s = sections; s && (s->flags & TYPE_PROGBITS);
          h++, s = s->next)
diff --git a/output/outelf32.c b/output/outelf32.c
index 7dce1658..6902beaf 100644
--- a/output/outelf32.c
+++ b/output/outelf32.c
@@ -461,8 +461,8 @@ static void elf_deflabel(char *name, int32_t segment, int64_t offset,
     bool special_used = false;
 
 #if defined(DEBUG) && DEBUG>2
-    fprintf(stderr,
-            " elf_deflabel: %s, seg=%ld, off=%ld, is_global=%d, %s\n",
+    nasm_error(ERR_DEBUG,
+            " elf_deflabel: %s, seg=%"PRIx32", off=%"PRIx64", is_global=%d, %s\n",
             name, segment, offset, is_global, special);
 #endif
     if (name[0] == '.' && name[1] == '.' && name[2] != '@') {
diff --git a/output/outelf64.c b/output/outelf64.c
index 5ccdf51c..53bc4c5a 100644
--- a/output/outelf64.c
+++ b/output/outelf64.c
@@ -386,7 +386,7 @@ static int32_t elf_section_names(char *name, int pass, int *bits)
             if (align == 0)
                 align = 1;
             if ((align - 1) & align) {  /* means it's not a power of two */
-                nasm_error(ERR_NONFATAL, "section alignment %d is not"
+                nasm_error(ERR_NONFATAL, "section alignment %"PRId64" is not"
                       " a power of two", align);
                 align = 1;
             }
@@ -465,8 +465,8 @@ static void elf_deflabel(char *name, int32_t segment, int64_t offset,
     bool special_used = false;
 
 #if defined(DEBUG) && DEBUG>2
-    fprintf(stderr,
-            " elf_deflabel: %s, seg=%x, off=%x, is_global=%d, %s\n",
+    nasm_error(ERR_DEBUG,
+            " elf_deflabel: %s, seg=%"PRIx32", off=%"PRIx64", is_global=%d, %s\n",
             name, segment, offset, is_global, special);
 #endif
     if (name[0] == '.' && name[1] == '.' && name[2] != '@') {
@@ -792,12 +792,14 @@ static void elf_out(int32_t segto, const void *data,
     zero = 0;
 
 #if defined(DEBUG) && DEBUG>2
-    if (data) fprintf(stderr,
-            " elf_out line: %d type: %x seg: %d segto: %d bytes: %x data: %"PRIx64"\n",
-               currentline, type, segment, segto, size, *(int64_t *)data);
-    else fprintf(stderr,
-            " elf_out line: %d type: %x seg: %d segto: %d bytes: %x\n",
-               currentline, type, segment, segto, size);
+    if (data)
+        nasm_error(ERR_DEBUG,
+                   " elf_out line: %d type: %x seg: %"PRIx32" segto: %"PRIx32" bytes: %"PRIx64" data: %"PRIx64"\n",
+                   currentline, type, segment, segto, size, *(int64_t *)data);
+    else
+        nasm_error(ERR_DEBUG,
+                   " elf_out line: %d type: %x seg: %"PRIx32" segto: %"PRIx32" bytes: %"PRIx64"\n",
+                   currentline, type, segment, segto, size);
 #endif
 
     /*
diff --git a/output/outobj.c b/output/outobj.c
index b8499ab9..87846fbd 100644
--- a/output/outobj.c
+++ b/output/outobj.c
@@ -774,8 +774,8 @@ static void obj_deflabel(char *name, int32_t segment,
     bool used_special = false;   /* have we used the special text? */
 
 #if defined(DEBUG) && DEBUG>2
-    fprintf(stderr,
-            " obj_deflabel: %s, seg=%ld, off=%ld, is_global=%d, %s\n",
+    nasm_error(ERR_DEBUG,
+            " obj_deflabel: %s, seg=%"PRIx32", off=%"PRIx64", is_global=%d, %s\n",
             name, segment, offset, is_global, special);
 #endif
 
@@ -1288,7 +1288,7 @@ static int32_t obj_segment(char *name, int pass, int *bits)
      * by sponging off the label manager.
      */
 #if defined(DEBUG) && DEBUG>=3
-    fprintf(stderr, " obj_segment: < %s >, pass=%d, *bits=%d\n",
+    nasm_error(ERR_DEBUG, " obj_segment: < %s >, pass=%d, *bits=%d\n",
             name, pass, *bits);
 #endif
     if (!name) {
diff --git a/parser.c b/parser.c
index 2ff6e36e..88cb937c 100644
--- a/parser.c
+++ b/parser.c
@@ -283,7 +283,7 @@ restart_parse:
             } else {
                 result->times = value->value;
                 if (value->value < 0 && pass0 == 2) {
-                    nasm_error(ERR_NONFATAL, "TIMES value %d is negative",
+                    nasm_error(ERR_NONFATAL, "TIMES value %"PRId64" is negative",
                           value->value);
                     result->times = 0;
                 }
@@ -531,11 +531,11 @@ restart_parse:
                 nasm_error(ERR_NONFATAL, "`incbin' expects a file name");
             else if (result->eops->next &&
                      result->eops->next->type != EOT_DB_NUMBER)
-                nasm_error(ERR_NONFATAL, "`incbin': second parameter is",
+                nasm_error(ERR_NONFATAL, "`incbin': second parameter is"
                       " non-numeric");
             else if (result->eops->next && result->eops->next->next &&
                      result->eops->next->next->type != EOT_DB_NUMBER)
-                nasm_error(ERR_NONFATAL, "`incbin': third parameter is",
+                nasm_error(ERR_NONFATAL, "`incbin': third parameter is"
                       " non-numeric");
             else if (result->eops->next && result->eops->next->next &&
                      result->eops->next->next->next)