diff -r b7e2e1d7ed22 -r 85859399a0cc src/printf.c
--- a/src/printf.c	Tue Jan 16 23:12:43 2024 +0100
+++ b/src/printf.c	Tue Jan 16 23:13:01 2024 +0100
@@ -127,3 +127,73 @@
     return s;
 }
 
+int cx_sprintf_a(CxAllocator *alloc, char **str, size_t len, const char *fmt, ... ) {
+    va_list ap;
+    va_start(ap, fmt);
+    int ret = cx_vsprintf_a(alloc, str, len, fmt, ap);
+    va_end(ap);
+    return ret;
+}
+
+int cx_vsprintf_a(CxAllocator *alloc, char **str, size_t len, const char *fmt, va_list ap) {
+    va_list ap2;
+    va_copy(ap2, ap);
+    int ret = vsnprintf(*str, len, fmt, ap);
+    if (ret < 0 || ((unsigned)ret) < len) {
+        va_end(ap2);
+        return ret;
+    } else {
+        unsigned newlen = ret + 1;
+        char *ptr = cxRealloc(alloc, *str, newlen);
+        if (ptr) {
+            int newret = vsnprintf(ptr, newlen, fmt, ap2);
+            va_end(ap2);
+            if (newret < 0) {
+                cxFree(alloc, ptr);
+                return ret;
+            } else {
+                *str = ptr;
+                return newret;
+            }
+        } else {
+            va_end(ap2);
+            return ret;
+        }
+    }
+}
+
+int cx_sprintf_sa(CxAllocator *alloc, char *buf, size_t len, char **str, const char *fmt, ... ) {
+    va_list ap;
+    va_start(ap, fmt);
+    int ret = cx_vsprintf_sa(alloc, buf, len, str, fmt, ap);
+    va_end(ap);
+    return ret;
+}
+
+int cx_vsprintf_sa(CxAllocator *alloc, char *buf, size_t len, char **str, const char *fmt, va_list ap) {
+    va_list ap2;
+    va_copy(ap2, ap);
+    int ret = vsnprintf(buf, len, fmt, ap);
+    *str = buf;
+    if (ret < 0 || ((unsigned)ret) < len) {
+        va_end(ap2);
+        return ret;
+    } else {
+        unsigned newlen = ret + 1;
+        char *ptr = cxMalloc(alloc, newlen);
+        if (ptr) {
+            int newret = vsnprintf(ptr, newlen, fmt, ap2);
+            va_end(ap2);
+            if (newret < 0) {
+                cxFree(alloc, ptr);
+                return ret;
+            } else {
+                *str = ptr;
+                return newret;
+            }
+        } else {
+            va_end(ap2);
+            return ret;
+        }
+    }
+}