all: remove c_variadic feature

src/bridge.c

@@ -0,0 +1,49 @@
+#define _GNU_SOURCE
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static char *fmt(const char *format, va_list args) {
+    char *line;
+    int ret = vasprintf(&line, format, args);
+    if (ret < 0) {
+        return 0;
+    } else {
+        return line;
+    }
+}
+
+void jay_libinput_log_handler(
+    void *libinput,
+    int priority,
+    const char *line
+);
+
+void jay_libinput_log_handler_bridge(
+    void *libinput,
+    int priority,
+    const char *format,
+    va_list args
+) {
+    char *line = fmt(format, args);
+    jay_libinput_log_handler(libinput, priority, line);
+    free(line);
+}
+
+void jay_xkbcommon_log_handler(
+    void *ctx,
+    int xkb_log_level,
+    const char *line
+);
+
+void jay_xkbcommon_log_handler_bridge(
+    void *ctx,
+    int xkb_log_level,
+    const char *format,
+    va_list args
+) {
+    char *line = fmt(format, args);
+    jay_xkbcommon_log_handler(ctx, xkb_log_level, line);
+    free(line);
+}