abstract out error logging a bit

just spitting things to stderr isn't always going to be good enough, so
let's at least provide one place to change that when necessary

10 files changed, 118 insertions, 126 deletions

diff --git a/Makefile b/Makefile
index 5b3933e..110ca62 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,8 @@ OBJ      = $(BUILD)runes.o \
 	   $(BUILD)screen.o \
 	   $(BUILD)config.o \
 	   $(BUILD)window-xlib.o \
-	   $(BUILD)pty-unix.o
+	   $(BUILD)pty-unix.o \
+	   $(BUILD)util.o
 LIBS     = cairo cairo-xlib libuv pangocairo
 CFLAGS  ?= -g -Wall -Wextra -Werror
 LDFLAGS ?= -g -Wall -Wextra -Werror
diff --git a/src/config.c b/src/config.c
index 689f042..b314522 100644
--- a/src/config.c
+++ b/src/config.c
@@ -1,4 +1,3 @@
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -390,7 +389,7 @@ static void runes_config_process_config_file(RunesTerm *t, FILE *config_file)
         kend = kbegin + strcspn(kbegin, " \t=");
         vbegin = kend + strspn(kend, " \t");
         if (*vbegin != '=') {
-            fprintf(stderr, "couldn't parse line: '%s'\n", line);
+            runes_warn("couldn't parse line: '%s'\n", line);
         }
         vbegin++;
         vbegin = vbegin + strspn(vbegin, " \t");
@@ -414,12 +413,11 @@ static void runes_config_process_args(RunesTerm *t, int argc, char *argv[])
                 i++;
             }
             else {
-                fprintf(
-                    stderr, "option found with no argument: '%s'\n", argv[i]);
+                runes_warn("option found with no argument: '%s'\n", argv[i]);
             }
         }
         else {
-            fprintf(stderr, "unknown argument: '%s'\n", argv[i]);
+            runes_warn("unknown argument: '%s'\n", argv[i]);
         }
     }
 }
@@ -482,7 +480,7 @@ static void runes_config_set(RunesTerm *t, char *key, char *val)
 
         i = atoi(&key[5]);
         if (key[5] < '0' || key[5] > '9' || i < 0 || i > 255) {
-            fprintf(stderr, "unknown option: '%s'\n", key);
+            runes_warn("unknown option: '%s'\n", key);
             return;
         }
         newcolor = runes_config_parse_color(val);
@@ -507,7 +505,7 @@ static void runes_config_set(RunesTerm *t, char *key, char *val)
         config->cmd = runes_config_parse_string(val);
     }
     else {
-        fprintf(stderr, "unknown option: '%s'\n", key);
+        runes_warn("unknown option: '%s'\n", key);
     }
 }
 
@@ -520,7 +518,7 @@ static char runes_config_parse_bool(char *val)
         return 0;
     }
     else {
-        fprintf(stderr, "unknown boolean value: '%s'\n", val);
+        runes_warn("unknown boolean value: '%s'\n", val);
         return 0;
     }
 }
@@ -528,7 +526,7 @@ static char runes_config_parse_bool(char *val)
 static int runes_config_parse_uint(char *val)
 {
     if (strspn(val, "0123456789") != strlen(val)) {
-        fprintf(stderr, "unknown unsigned integer value: '%s'\n", val);
+        runes_warn("unknown unsigned integer value: '%s'\n", val);
     }
 
     return atoi(val);
@@ -544,7 +542,7 @@ static cairo_pattern_t *runes_config_parse_color(char *val)
     int r, g, b;
 
     if (strlen(val) != 7 || sscanf(val, "#%2x%2x%2x", &r, &g, &b) != 3) {
-        fprintf(stderr, "unknown color value: '%s'\n", val);
+        runes_warn("unknown color value: '%s'\n", val);
         return NULL;
     }
 
diff --git a/src/parser.c b/src/parser.c
index 193c747..388097d 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -1187,8 +1187,8 @@ case 49:
 YY_RULE_SETUP
 #line 182 "src/parser.l"
 {
-    fprintf(
-        stderr, "unhandled CSI sequence: \\033%*s\\%hho\n",
+    runes_warn(
+        "unhandled CSI sequence: \\033%*s\\%hho\n",
         (int)yyleng - 2, yytext + 1, yytext[yyleng - 1]);
 }
 	YY_BREAK
@@ -1196,8 +1196,8 @@ case 50:
 YY_RULE_SETUP
 #line 188 "src/parser.l"
 {
-    fprintf(
-        stderr, "unhandled CSI sequence: \\033%*s\n",
+    runes_warn(
+        "unhandled CSI sequence: \\033%*s\n",
         (int)yyleng - 1, yytext + 1);
 }
 	YY_BREAK
@@ -1206,8 +1206,8 @@ case 51:
 YY_RULE_SETUP
 #line 194 "src/parser.l"
 {
-    fprintf(
-        stderr, "unhandled OSC sequence: \\033%*s\\%hho\n",
+    runes_warn(
+        "unhandled OSC sequence: \\033%*s\\%hho\n",
         (int)yyleng - 2, yytext + 1, yytext[yyleng - 1]);
 }
 	YY_BREAK
@@ -1215,8 +1215,8 @@ case 52:
 YY_RULE_SETUP
 #line 200 "src/parser.l"
 {
-    fprintf(
-        stderr, "unhandled OSC sequence: \\033%*s\n",
+    runes_warn(
+        "unhandled OSC sequence: \\033%*s\n",
         (int)yyleng - 1, yytext + 1);
 }
 	YY_BREAK
@@ -1225,15 +1225,15 @@ case 53:
 YY_RULE_SETUP
 #line 206 "src/parser.l"
 {
-    fprintf(stderr, "unhandled escape sequence: \\%hho\n", yytext[1]);
+    runes_warn("unhandled escape sequence: \\%hho\n", yytext[1]);
 }
 	YY_BREAK
 case 54:
 YY_RULE_SETUP
 #line 210 "src/parser.l"
 {
-    fprintf(
-        stderr, "unhandled escape sequence: %*s\n",
+    runes_warn(
+        "unhandled escape sequence: %*s\n",
         (int)yyleng - 1, yytext + 1);
 }
 	YY_BREAK
@@ -1242,14 +1242,14 @@ case 55:
 YY_RULE_SETUP
 #line 216 "src/parser.l"
 {
-    fprintf(stderr, "unhandled control character: \\%hho\n", yytext[0]);
+    runes_warn("unhandled control character: \\%hho\n", yytext[0]);
 }
 	YY_BREAK
 case 56:
 YY_RULE_SETUP
 #line 220 "src/parser.l"
 {
-    fprintf(stderr, "invalid utf8 byte: \\%hho\n", yytext[0]);
+    runes_warn("invalid utf8 byte: \\%hho\n", yytext[0]);
 }
 	YY_BREAK
 case 57:
@@ -2450,7 +2450,7 @@ static void runes_parser_extract_sm_params(
     *nparams = 0;
     while ((size_t)(pos - buf) < len) {
         if (*nparams >= RUNES_PARSER_CSI_MAX_PARAMS) {
-            fprintf(stderr, "max CSI parameter length exceeded\n");
+            runes_warn("max CSI parameter length exceeded\n");
             break;
         }
 
@@ -2549,7 +2549,7 @@ static void runes_parser_handle_ed(RunesTerm *t, char *buf, size_t len)
         runes_screen_clear_screen(t);
         break;
     default:
-        fprintf(stderr, "unknown ED parameter %d\n", params[0]);
+        runes_warn("unknown ED parameter %d\n", params[0]);
         break;
     }
 }
@@ -2570,7 +2570,7 @@ static void runes_parser_handle_el(RunesTerm *t, char *buf, size_t len)
         runes_screen_kill_line(t);
         break;
     default:
-        fprintf(stderr, "unknown EL parameter %d\n", params[0]);
+        runes_warn("unknown EL parameter %d\n", params[0]);
         break;
     }
 }
@@ -2615,9 +2615,7 @@ static void runes_parser_handle_sm(RunesTerm *t, char *buf, size_t len)
                     /* do nothing, no idea what this is even for */
                     break;
                 default:
-                    fprintf(
-                        stderr, "unknown SM parameter: %d\n",
-                        params[i]);
+                    runes_warn("unknown SM parameter: %d\n", params[i]);
                     break;
             }
             break;
@@ -2640,16 +2638,13 @@ static void runes_parser_handle_sm(RunesTerm *t, char *buf, size_t len)
                 runes_screen_use_alternate_buffer(t);
                 break;
             default:
-                fprintf(
-                    stderr, "unknown SM parameter: %c%d\n",
-                    modes[i], params[i]);
+                runes_warn(
+                    "unknown SM parameter: %c%d\n", modes[i], params[i]);
                 break;
             }
             break;
         default:
-            fprintf(
-                stderr, "unknown SM parameter: %c%d\n",
-                modes[i], params[i]);
+            runes_warn("unknown SM parameter: %c%d\n", modes[i], params[i]);
             break;
         }
     }
@@ -2669,9 +2664,7 @@ static void runes_parser_handle_rm(RunesTerm *t, char *buf, size_t len)
                     /* do nothing, no idea what this is even for */
                     break;
                 default:
-                    fprintf(
-                        stderr, "unknown RM parameter: %d\n",
-                        params[i]);
+                    runes_warn("unknown RM parameter: %d\n", params[i]);
                     break;
             }
             break;
@@ -2694,16 +2687,13 @@ static void runes_parser_handle_rm(RunesTerm *t, char *buf, size_t len)
                 runes_screen_use_normal_buffer(t);
                 break;
             default:
-                fprintf(
-                    stderr, "unknown RM parameter: %c%d\n",
-                    modes[i], params[i]);
+                runes_warn(
+                    "unknown RM parameter: %c%d\n", modes[i], params[i]);
                 break;
             }
             break;
         default:
-            fprintf(
-                stderr, "unknown RM parameter: %c%d\n",
-                modes[i], params[i]);
+            runes_warn("unknown RM parameter: %c%d\n", modes[i], params[i]);
             break;
         }
     }
@@ -2753,8 +2743,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
         case 38: {
             i++;
             if (i >= nparams) {
-                fprintf(
-                    stderr, "unknown SGR parameter: %d (too few parameters)\n",
+                runes_warn(
+                    "unknown SGR parameter: %d (too few parameters)\n",
                     params[i - 1]);
                 break;
             }
@@ -2763,8 +2753,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 2:
                 i += 3;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 4], params[i - 3]);
                     break;
@@ -2775,8 +2764,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 5:
                 i++;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 2], params[i - 1]);
                     break;
@@ -2785,8 +2773,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
                 break;
             default:
                 i++;
-                fprintf(
-                    stderr, "unknown SGR parameter: %d;%d\n",
+                runes_warn(
+                    "unknown SGR parameter: %d;%d\n",
                     params[i - 2], params[i - 1]);
                 break;
             }
@@ -2802,8 +2790,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
         case 48: {
             i++;
             if (i >= nparams) {
-                fprintf(
-                    stderr, "unknown SGR parameter: %d (too few parameters)\n",
+                runes_warn(
+                    "unknown SGR parameter: %d (too few parameters)\n",
                     params[i - 1]);
                 break;
             }
@@ -2812,8 +2800,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 2:
                 i += 3;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 4], params[i - 3]);
                     break;
@@ -2824,8 +2811,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 5:
                 i++;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 2], params[i - 1]);
                     break;
@@ -2834,8 +2820,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
                 break;
             default:
                 i++;
-                fprintf(
-                    stderr, "unknown SGR parameter: %d;%d\n",
+                runes_warn(
+                    "unknown SGR parameter: %d;%d\n",
                     params[i - 2], params[i - 1]);
                 break;
             }
@@ -2853,7 +2839,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             runes_screen_set_bg_color(t, params[i] - 92);
             break;
         default:
-            fprintf(stderr, "unknown SGR parameter: %d\n", params[i]);
+            runes_warn("unknown SGR parameter: %d\n", params[i]);
             break;
         }
     }
@@ -2883,14 +2869,14 @@ static void runes_parser_handle_decsed(RunesTerm *t, char *buf, size_t len)
         break;
     case 1:
         /* XXX */
-        fprintf(stderr, "unhandled DECSED parameter 1\n");
+        runes_warn("unhandled DECSED parameter 1\n");
         break;
     case 2:
         /* XXX not quite correct */
         runes_screen_clear_screen(t);
         break;
     default:
-        fprintf(stderr, "unknown DECSED parameter %d\n", params[0]);
+        runes_warn("unknown DECSED parameter %d\n", params[0]);
         break;
     }
 }
@@ -2907,14 +2893,14 @@ static void runes_parser_handle_decsel(RunesTerm *t, char *buf, size_t len)
         break;
     case 1:
         /* XXX */
-        fprintf(stderr, "unhandled DECSEL parameter 1\n");
+        runes_warn("unhandled DECSEL parameter 1\n");
         break;
     case 2:
         /* XXX */
-        fprintf(stderr, "unhandled DECSEL parameter 2\n");
+        runes_warn("unhandled DECSEL parameter 2\n");
         break;
     default:
-        fprintf(stderr, "unknown DECSEL parameter %d\n", params[0]);
+        runes_warn("unknown DECSEL parameter %d\n", params[0]);
         break;
     }
 }
diff --git a/src/parser.l b/src/parser.l
index 7c3ef02..b22c7a1 100644
--- a/src/parser.l
+++ b/src/parser.l
@@ -180,45 +180,45 @@ static void runes_parser_handle_text(RunesTerm *t, char *text, size_t len);
 <<EOF>> return 0;
 
 {CSI}[<=?]?{CSIPARAMS}{CTRL} {
-    fprintf(
-        stderr, "unhandled CSI sequence: \\033%*s\\%hho\n",
+    runes_warn(
+        "unhandled CSI sequence: \\033%*s\\%hho\n",
         (int)yyleng - 2, yytext + 1, yytext[yyleng - 1]);
 }
 
 {CSI}[<=?]?{CSIPARAMS}{CHAR} {
-    fprintf(
-        stderr, "unhandled CSI sequence: \\033%*s\n",
+    runes_warn(
+        "unhandled CSI sequence: \\033%*s\n",
         (int)yyleng - 1, yytext + 1);
 }
 
 {OSC}{CTRL} {
-    fprintf(
-        stderr, "unhandled OSC sequence: \\033%*s\\%hho\n",
+    runes_warn(
+        "unhandled OSC sequence: \\033%*s\\%hho\n",
         (int)yyleng - 2, yytext + 1, yytext[yyleng - 1]);
 }
 
 {OSC}{CHAR} {
-    fprintf(
-        stderr, "unhandled OSC sequence: \\033%*s\n",
+    runes_warn(
+        "unhandled OSC sequence: \\033%*s\n",
         (int)yyleng - 1, yytext + 1);
 }
 
 {ESC}{CTRL} {
-    fprintf(stderr, "unhandled escape sequence: \\%hho\n", yytext[1]);
+    runes_warn("unhandled escape sequence: \\%hho\n", yytext[1]);
 }
 
 {ESC}{CHAR} {
-    fprintf(
-        stderr, "unhandled escape sequence: %*s\n",
+    runes_warn(
+        "unhandled escape sequence: %*s\n",
         (int)yyleng - 1, yytext + 1);
 }
 
 {CTRL} {
-    fprintf(stderr, "unhandled control character: \\%hho\n", yytext[0]);
+    runes_warn("unhandled control character: \\%hho\n", yytext[0]);
 }
 
 (?s:.) {
-    fprintf(stderr, "invalid utf8 byte: \\%hho\n", yytext[0]);
+    runes_warn("invalid utf8 byte: \\%hho\n", yytext[0]);
 }
 
 %%
@@ -320,7 +320,7 @@ static void runes_parser_extract_sm_params(
     *nparams = 0;
     while ((size_t)(pos - buf) < len) {
         if (*nparams >= RUNES_PARSER_CSI_MAX_PARAMS) {
-            fprintf(stderr, "max CSI parameter length exceeded\n");
+            runes_warn("max CSI parameter length exceeded\n");
             break;
         }
 
@@ -419,7 +419,7 @@ static void runes_parser_handle_ed(RunesTerm *t, char *buf, size_t len)
         runes_screen_clear_screen(t);
         break;
     default:
-        fprintf(stderr, "unknown ED parameter %d\n", params[0]);
+        runes_warn("unknown ED parameter %d\n", params[0]);
         break;
     }
 }
@@ -440,7 +440,7 @@ static void runes_parser_handle_el(RunesTerm *t, char *buf, size_t len)
         runes_screen_kill_line(t);
         break;
     default:
-        fprintf(stderr, "unknown EL parameter %d\n", params[0]);
+        runes_warn("unknown EL parameter %d\n", params[0]);
         break;
     }
 }
@@ -485,9 +485,7 @@ static void runes_parser_handle_sm(RunesTerm *t, char *buf, size_t len)
                     /* do nothing, no idea what this is even for */
                     break;
                 default:
-                    fprintf(
-                        stderr, "unknown SM parameter: %d\n",
-                        params[i]);
+                    runes_warn("unknown SM parameter: %d\n", params[i]);
                     break;
             }
             break;
@@ -510,16 +508,13 @@ static void runes_parser_handle_sm(RunesTerm *t, char *buf, size_t len)
                 runes_screen_use_alternate_buffer(t);
                 break;
             default:
-                fprintf(
-                    stderr, "unknown SM parameter: %c%d\n",
-                    modes[i], params[i]);
+                runes_warn(
+                    "unknown SM parameter: %c%d\n", modes[i], params[i]);
                 break;
             }
             break;
         default:
-            fprintf(
-                stderr, "unknown SM parameter: %c%d\n",
-                modes[i], params[i]);
+            runes_warn("unknown SM parameter: %c%d\n", modes[i], params[i]);
             break;
         }
     }
@@ -539,9 +534,7 @@ static void runes_parser_handle_rm(RunesTerm *t, char *buf, size_t len)
                     /* do nothing, no idea what this is even for */
                     break;
                 default:
-                    fprintf(
-                        stderr, "unknown RM parameter: %d\n",
-                        params[i]);
+                    runes_warn("unknown RM parameter: %d\n", params[i]);
                     break;
             }
             break;
@@ -564,16 +557,13 @@ static void runes_parser_handle_rm(RunesTerm *t, char *buf, size_t len)
                 runes_screen_use_normal_buffer(t);
                 break;
             default:
-                fprintf(
-                    stderr, "unknown RM parameter: %c%d\n",
-                    modes[i], params[i]);
+                runes_warn(
+                    "unknown RM parameter: %c%d\n", modes[i], params[i]);
                 break;
             }
             break;
         default:
-            fprintf(
-                stderr, "unknown RM parameter: %c%d\n",
-                modes[i], params[i]);
+            runes_warn("unknown RM parameter: %c%d\n", modes[i], params[i]);
             break;
         }
     }
@@ -623,8 +613,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
         case 38: {
             i++;
             if (i >= nparams) {
-                fprintf(
-                    stderr, "unknown SGR parameter: %d (too few parameters)\n",
+                runes_warn(
+                    "unknown SGR parameter: %d (too few parameters)\n",
                     params[i - 1]);
                 break;
             }
@@ -633,8 +623,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 2:
                 i += 3;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 4], params[i - 3]);
                     break;
@@ -645,8 +634,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 5:
                 i++;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 2], params[i - 1]);
                     break;
@@ -655,8 +643,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
                 break;
             default:
                 i++;
-                fprintf(
-                    stderr, "unknown SGR parameter: %d;%d\n",
+                runes_warn(
+                    "unknown SGR parameter: %d;%d\n",
                     params[i - 2], params[i - 1]);
                 break;
             }
@@ -672,8 +660,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
         case 48: {
             i++;
             if (i >= nparams) {
-                fprintf(
-                    stderr, "unknown SGR parameter: %d (too few parameters)\n",
+                runes_warn(
+                    "unknown SGR parameter: %d (too few parameters)\n",
                     params[i - 1]);
                 break;
             }
@@ -682,8 +670,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 2:
                 i += 3;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 4], params[i - 3]);
                     break;
@@ -694,8 +681,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             case 5:
                 i++;
                 if (i >= nparams) {
-                    fprintf(
-                        stderr,
+                    runes_warn(
                         "unknown SGR parameter: %d;%d (too few parameters)\n",
                         params[i - 2], params[i - 1]);
                     break;
@@ -704,8 +690,8 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
                 break;
             default:
                 i++;
-                fprintf(
-                    stderr, "unknown SGR parameter: %d;%d\n",
+                runes_warn(
+                    "unknown SGR parameter: %d;%d\n",
                     params[i - 2], params[i - 1]);
                 break;
             }
@@ -723,7 +709,7 @@ static void runes_parser_handle_sgr(RunesTerm *t, char *buf, size_t len)
             runes_screen_set_bg_color(t, params[i] - 92);
             break;
         default:
-            fprintf(stderr, "unknown SGR parameter: %d\n", params[i]);
+            runes_warn("unknown SGR parameter: %d\n", params[i]);
             break;
         }
     }
@@ -753,14 +739,14 @@ static void runes_parser_handle_decsed(RunesTerm *t, char *buf, size_t len)
         break;
     case 1:
         /* XXX */
-        fprintf(stderr, "unhandled DECSED parameter 1\n");
+        runes_warn("unhandled DECSED parameter 1\n");
         break;
     case 2:
         /* XXX not quite correct */
         runes_screen_clear_screen(t);
         break;
     default:
-        fprintf(stderr, "unknown DECSED parameter %d\n", params[0]);
+        runes_warn("unknown DECSED parameter %d\n", params[0]);
         break;
     }
 }
@@ -777,14 +763,14 @@ static void runes_parser_handle_decsel(RunesTerm *t, char *buf, size_t len)
         break;
     case 1:
         /* XXX */
-        fprintf(stderr, "unhandled DECSEL parameter 1\n");
+        runes_warn("unhandled DECSEL parameter 1\n");
         break;
     case 2:
         /* XXX */
-        fprintf(stderr, "unhandled DECSEL parameter 2\n");
+        runes_warn("unhandled DECSEL parameter 2\n");
         break;
     default:
-        fprintf(stderr, "unknown DECSEL parameter %d\n", params[0]);
+        runes_warn("unknown DECSEL parameter %d\n", params[0]);
         break;
     }
 }
diff --git a/src/pty-unix.c b/src/pty-unix.c
index 82a3809..b43ae6f 100644
--- a/src/pty-unix.c
+++ b/src/pty-unix.c
@@ -1,5 +1,6 @@
 #define _XOPEN_SOURCE 600
 #include <fcntl.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
diff --git a/src/runes.h b/src/runes.h
index 05398e9..18d6174 100644
--- a/src/runes.h
+++ b/src/runes.h
@@ -28,6 +28,8 @@ struct runes_loop_data {
     RunesTerm *t;
 };
 
+#include "util.h"
+
 #include "window-xlib.h"
 #include "pty-unix.h"
 
diff --git a/src/screen.c b/src/screen.c
index 57b536d..a9ffb3e 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -446,7 +446,7 @@ void runes_screen_set_scroll_region(
     RunesScreen *scr = &t->scr;
 
     if (left > 0 || right < scr->grid->max.col - 1) {
-        fprintf(stderr, "vertical scroll regions not yet implemented\n");
+        runes_warn("vertical scroll regions not yet implemented\n");
     }
 
     if (top > bottom) {
diff --git a/src/util.c b/src/util.c
new file mode 100644
index 0000000..d87fd72
--- /dev/null
+++ b/src/util.c
@@ -0,0 +1,13 @@
+#include <stdarg.h>
+#include <stdio.h>
+
+#include "runes.h"
+
+void runes_warn(const char *fmt, ...)
+{
+    va_list ap;
+    va_start(ap, fmt);
+    /* XXX make this do something else on windows */
+    vfprintf(stderr, fmt, ap);
+    va_end(ap);
+}
diff --git a/src/util.h b/src/util.h
new file mode 100644
index 0000000..f542261
--- /dev/null
+++ b/src/util.h
@@ -0,0 +1,6 @@
+#ifndef _RUNES_UTIL_H
+#define _RUNES_UTIL_H
+
+void runes_warn(const char *fmt, ...);
+
+#endif
diff --git a/src/window-xlib.c b/src/window-xlib.c
index 2c36e44..cc9ec7e 100644
--- a/src/window-xlib.c
+++ b/src/window-xlib.c
@@ -1,5 +1,4 @@
 #include <cairo-xlib.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <X11/cursorfont.h>
@@ -167,7 +166,7 @@ void runes_window_backend_create_window(RunesTerm *t, int argc, char *argv[])
         NULL
     );
     if (w->ic == NULL) {
-        fprintf(stderr, "failed\n");
+        runes_warn("failed\n");
         exit(1);
     }