format utility improvements

src/format.cpp

@@ -2,6 +2,8 @@
 
 #include <array>
 #include <cmath>
+#include <cstdio>
+#include <cstdlib>
 
 // Copied from simdjson
 namespace {
@@ -980,30 +982,25 @@ std::string_view format(ArenaAllocator &arena, const char *fmt, ...) {
                             static_cast<std::size_t>(bytes_written));
   }
 
-  // Fallback: Two-pass approach when speculative formatting fails
-  va_list args_fallback;
-  va_start(args_fallback, fmt);
-  const int required_size = std::vsnprintf(nullptr, 0, fmt, args_fallback);
-  va_end(args_fallback);
-
-  if (required_size < 0) {
-    // Handle formatting error by returning empty string_view
-    return std::string_view{};
+  // Fallback: vsnprintf failed or didn't fit, use two-pass approach
+  if (bytes_written < 0) {
+    std::fprintf(stderr, "vsnprintf failed in format()\n");
+    std::abort();
   }
 
-  // Allocate exact buffer size needed (+1 for null terminator)
-  const int buffer_size = required_size + 1;
+  // We know bytes_written is the required size
+  const int buffer_size = bytes_written + 1;
   char *result = arena.allocate<char>(static_cast<uint32_t>(buffer_size));
 
   // Format into the exact-sized buffer
-  va_start(args_fallback, fmt);
-  const int actual_size = std::vsnprintf(
-      result, static_cast<std::size_t>(buffer_size), fmt, args_fallback);
-  va_end(args_fallback);
+  va_start(args, fmt);
+  const int actual_size =
+      std::vsnprintf(result, static_cast<std::size_t>(buffer_size), fmt, args);
+  va_end(args);
 
   if (actual_size < 0 || actual_size >= buffer_size) {
-    // Handle formatting error
-    return std::string_view{};
+    std::fprintf(stderr, "vsnprintf failed in format() fallback\n");
+    std::abort();
   }
 
   // Shrink to exclude null terminator for string_view