Add xsnprintf() and remove some unnecessary strlen(3) calls

csi.c

@@ -23,6 +23,7 @@
 #include "version.h"
 #include "vt.h"
 #include "xmalloc.h"
+#include "xsnprintf.h"
 
 #define UNHANDLED()        LOG_DBG("unhandled: %s", csi_as_string(term, final, -1))
 #define UNHANDLED_SGR(idx) LOG_DBG("unhandled: %s", csi_as_string(term, 'm', idx))
@@ -1204,9 +1205,9 @@ csi_dispatch(struct terminal *term, uint8_t final)
 
                 if (x >= 0 && y >= 0) {
                     char reply[64];
-                    snprintf(reply, sizeof(reply), "\033[3;%d;%dt",
+                    size_t n = xsnprintf(reply, sizeof(reply), "\033[3;%d;%dt",
                              x / term->scale, y / term->scale);
-                    term_to_slave(term, reply, strlen(reply));
+                    term_to_slave(term, reply, n);
                 }
                 break;
             }
@@ -1235,9 +1236,9 @@ csi_dispatch(struct terminal *term, uint8_t final)
 
                 if (width >= 0 && height >= 0) {
                     char reply[64];
-                    snprintf(reply, sizeof(reply), "\033[4;%d;%dt",
+                    size_t n = xsnprintf(reply, sizeof(reply), "\033[4;%d;%dt",
                              height / term->scale, width / term->scale);
-                    term_to_slave(term, reply, strlen(reply));
+                    term_to_slave(term, reply, n);
                 }
                 break;
             }
@@ -1245,10 +1246,10 @@ csi_dispatch(struct terminal *term, uint8_t final)
             case 15:   /* report screen size in pixels */
                 tll_foreach(term->window->on_outputs, it) {
                     char reply[64];
-                    snprintf(reply, sizeof(reply), "\033[5;%d;%dt",
+                    size_t n = xsnprintf(reply, sizeof(reply), "\033[5;%d;%dt",
                              it->item->dim.px_scaled.height,
                              it->item->dim.px_scaled.width);
-                    term_to_slave(term, reply, strlen(reply));
+                    term_to_slave(term, reply, n);
                     break;
                 }
 
@@ -1258,28 +1259,28 @@ csi_dispatch(struct terminal *term, uint8_t final)
 
             case 16: { /* report cell size in pixels */
                 char reply[64];
-                snprintf(reply, sizeof(reply), "\033[6;%d;%dt",
+                size_t n = xsnprintf(reply, sizeof(reply), "\033[6;%d;%dt",
                          term->cell_height / term->scale,
                          term->cell_width / term->scale);
-                term_to_slave(term, reply, strlen(reply));
+                term_to_slave(term, reply, n);
                 break;
             }
 
             case 18: { /* text area size in chars */
                 char reply[64];
-                snprintf(reply, sizeof(reply), "\033[8;%d;%dt",
+                size_t n = xsnprintf(reply, sizeof(reply), "\033[8;%d;%dt",
                          term->rows, term->cols);
-                term_to_slave(term, reply, strlen(reply));
+                term_to_slave(term, reply, n);
                 break;
             }
 
             case 19: { /* report screen size in chars */
                 tll_foreach(term->window->on_outputs, it) {
                     char reply[64];
-                    snprintf(reply, sizeof(reply), "\033[9;%d;%dt",
+                    size_t n = xsnprintf(reply, sizeof(reply), "\033[9;%d;%dt",
                              it->item->dim.px_real.height / term->cell_height / term->scale,
                              it->item->dim.px_real.width / term->cell_width / term->scale);
-                    term_to_slave(term, reply, strlen(reply));
+                    term_to_slave(term, reply, n);
                     break;
                 }
 
@@ -1341,9 +1342,9 @@ csi_dispatch(struct terminal *term, uint8_t final)
                      * terminfo says the receiver of the reply should
                      * decrement, hence we must add 1 */
                     char reply[64];
-                    snprintf(reply, sizeof(reply), "\x1b[%d;%dR",
+                    size_t n = xsnprintf(reply, sizeof(reply), "\x1b[%d;%dR",
                              row + 1, term->grid->cursor.point.col + 1);
-                    term_to_slave(term, reply, strlen(reply));
+                    term_to_slave(term, reply, n);
                     break;
                 }
 
@@ -1468,10 +1469,10 @@ csi_dispatch(struct terminal *term, uint8_t final)
                 static_assert(FOOT_PATCH < 100, "Patch version must not exceed 99");
 
                 char reply[64];
-                snprintf(reply, sizeof(reply), "\033[>1;%02u%02u%02u;0c",
+                size_t n = xsnprintf(reply, sizeof(reply), "\033[>1;%02u%02u%02u;0c",
                          FOOT_MAJOR, FOOT_MINOR, FOOT_PATCH);
 
-                term_to_slave(term, reply, strlen(reply));
+                term_to_slave(term, reply, n);
                 break;
 
         case 'm':
@@ -1625,8 +1626,8 @@ csi_dispatch(struct terminal *term, uint8_t final)
                 value = 0;
 
             char reply[32];
-            snprintf(reply, sizeof(reply), "\033[?%u;%u$y", param, value);
+            size_t n = xsnprintf(reply, sizeof(reply), "\033[?%u;%u$y", param, value);
-            term_to_slave(term, reply, strlen(reply));
+            term_to_slave(term, reply, n);
             break;
 
         }

input.c

@@ -37,6 +37,7 @@
 #include "util.h"
 #include "vt.h"
 #include "xmalloc.h"
+#include "xsnprintf.h"
 
 struct pipe_context {
     char *text;
@@ -974,8 +975,8 @@ key_press_release(struct seat *seat, struct terminal *term, uint32_t serial,
         assert(modify_param != 0);
 
         char reply[1024];
-        snprintf(reply, sizeof(reply), "\x1b[27;%d;%d~", modify_param, sym);
+        size_t n = xsnprintf(reply, sizeof(reply), "\x1b[27;%d;%d~", modify_param, sym);
-        term_to_slave(term, reply, strlen(reply));
+        term_to_slave(term, reply, n);
     }
 
     else {

main.c

@@ -31,6 +31,7 @@
 #include "util.h"
 #include "version.h"
 #include "xmalloc.h"
+#include "xsnprintf.h"
 
 static volatile sig_atomic_t aborted = 0;
 
@@ -127,9 +128,9 @@ print_pid(const char *pid_file, bool *unlink_at_exit)
 
     if (pid_fd >= 0) {
         char pid[32];
-        snprintf(pid, sizeof(pid), "%u\n", getpid());
+        size_t n = xsnprintf(pid, sizeof(pid), "%u\n", getpid());
 
-        ssize_t bytes = write(pid_fd, pid, strlen(pid));
+        ssize_t bytes = write(pid_fd, pid, n);
         close(pid_fd);
 
         if (bytes < 0) {

meson.build

@@ -112,6 +112,7 @@ misc = static_library(
   'misc.c', 'misc.h',
   'uri.c', 'uri.h',
   'xmalloc.c', 'xmalloc.h',
+  'xsnprintf.c', 'xsnprintf.h',
 )
 
 vtlib = static_library(

osc.c

@@ -17,6 +17,7 @@
 #include "uri.h"
 #include "vt.h"
 #include "xmalloc.h"
+#include "xsnprintf.h"
 
 #define UNHANDLED() LOG_DBG("unhandled: OSC: %.*s", (int)term->vt.osc.idx, term->vt.osc.data)
 
@@ -522,9 +523,9 @@ osc_dispatch(struct terminal *term)
                 uint8_t b = (color >>  0) & 0xff;
 
                 char reply[32];
-                snprintf(reply, sizeof(reply), "\033]4;%u;rgb:%02x/%02x/%02x\033\\",
+                size_t n = xsnprintf(reply, sizeof(reply), "\033]4;%u;rgb:%02x/%02x/%02x\033\\",
                          idx, r, g, b);
-                term_to_slave(term, reply, strlen(reply));
+                term_to_slave(term, reply, n);
             }
 
             else {
@@ -568,11 +569,11 @@ osc_dispatch(struct terminal *term)
              * E.g. for color 0xdcdccc we reply "\033]10;rgb:dc/dc/cc\033\\"
              */
             char reply[32];
-            snprintf(
+            size_t n = xsnprintf(
                 reply, sizeof(reply), "\033]%u;rgb:%02x/%02x/%02x\033\\",
                 param, r, g, b);
 
-            term_to_slave(term, reply, strlen(reply));
+            term_to_slave(term, reply, n);
             break;
         }
 
@@ -602,8 +603,8 @@ osc_dispatch(struct terminal *term)
             uint8_t b = (term->cursor_color.cursor >>  0) & 0xff;
 
             char reply[32];
-            snprintf(reply, sizeof(reply), "\033]12;rgb:%02x/%02x/%02x\033\\", r, g, b);
+            size_t n = xsnprintf(reply, sizeof(reply), "\033]12;rgb:%02x/%02x/%02x\033\\", r, g, b);
-            term_to_slave(term, reply, strlen(reply));
+            term_to_slave(term, reply, n);
             break;
         }
 

sixel.c

@@ -10,6 +10,7 @@
 #include "hsl.h"
 #include "util.h"
 #include "xmalloc.h"
+#include "xsnprintf.h"
 
 static size_t count;
 
@@ -1101,8 +1102,8 @@ void
 sixel_colors_report_current(struct terminal *term)
 {
     char reply[24];
-    snprintf(reply, sizeof(reply), "\033[?1;0;%uS", term->sixel.palette_size);
+    size_t n = xsnprintf(reply, sizeof(reply), "\033[?1;0;%uS", term->sixel.palette_size);
-    term_to_slave(term, reply, strlen(reply));
+    term_to_slave(term, reply, n);
     LOG_DBG("query response for current color count: %u", term->sixel.palette_size);
 }
 
@@ -1135,8 +1136,8 @@ void
 sixel_colors_report_max(struct terminal *term)
 {
     char reply[24];
-    snprintf(reply, sizeof(reply), "\033[?1;0;%uS", SIXEL_MAX_COLORS);
+    size_t n = xsnprintf(reply, sizeof(reply), "\033[?1;0;%uS", SIXEL_MAX_COLORS);
-    term_to_slave(term, reply, strlen(reply));
+    term_to_slave(term, reply, n);
     LOG_DBG("query response for max color count: %u", SIXEL_MAX_COLORS);
 }
 
@@ -1144,10 +1145,10 @@ void
 sixel_geometry_report_current(struct terminal *term)
 {
     char reply[64];
-    snprintf(reply, sizeof(reply), "\033[?2;0;%u;%uS",
+    size_t n = xsnprintf(reply, sizeof(reply), "\033[?2;0;%u;%uS",
              min(term->cols * term->cell_width, term->sixel.max_width),
              min(term->rows * term->cell_height, term->sixel.max_height));
-    term_to_slave(term, reply, strlen(reply));
+    term_to_slave(term, reply, n);
 
     LOG_DBG("query response for current sixel geometry: %ux%u",
             term->sixel.max_width, term->sixel.max_height);
@@ -1178,8 +1179,8 @@ sixel_geometry_report_max(struct terminal *term)
     unsigned max_height = term->rows * term->cell_height;
 
     char reply[64];
-    snprintf(reply, sizeof(reply), "\033[?2;0;%u;%uS", max_width, max_height);
+    size_t n = xsnprintf(reply, sizeof(reply), "\033[?2;0;%u;%uS", max_width, max_height);
-    term_to_slave(term, reply, strlen(reply));
+    term_to_slave(term, reply, n);
 
     LOG_DBG("query response for max sixel geometry: %ux%u",
             max_width, max_height);

xsnprintf.c

@@ -0,0 +1,36 @@
+#include "xsnprintf.h"
+
+#include <assert.h>
+#include <limits.h>
+#include <stdio.h>
+
+size_t
+xvsnprintf(char *buf, size_t n, const char *format, va_list ap)
+{
+    assert(n <= INT_MAX);
+    int len = vsnprintf(buf, n, format, ap);
+
+    /*
+     * ISO C11 §7.21.6.5 states:
+     * "The snprintf function returns the number of characters that
+     * would have been written had n been sufficiently large, not
+     * counting the terminating null character, or a negative value
+     * if an encoding error occurred. Thus, the null-terminated output
+     * has been completely written if and only if the returned value
+     * is nonnegative and less than n."
+     */
+    assert(len >= 0);
+    assert(len < (int)n);
+
+    return (size_t)len;
+}
+
+size_t
+xsnprintf(char *buf, size_t n, const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    size_t len = xvsnprintf(buf, n, format, ap);
+    va_end(ap);
+    return len;
+}

xsnprintf.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <stdarg.h>
+#include <stddef.h>
+#include "macros.h"
+
+size_t xsnprintf(char *buf, size_t len, const char *fmt, ...) PRINTF(3) NONNULL_ARGS;
+size_t xvsnprintf(char *buf, size_t len, const char *fmt, va_list ap) VPRINTF(3) NONNULL_ARGS;