adamdebreceni commented on a change in pull request #1057:
URL: https://github.com/apache/nifi-minifi-cpp/pull/1057#discussion_r635261808



##########
File path: libminifi/include/core/logging/Logger.h
##########
@@ -68,13 +69,32 @@ inline T conditional_conversion(T t) {
 }
 
 template<typename ... Args>
-inline std::string format_string(char const* format_str, Args&&... args) {
-  char buf[LOG_BUFFER_SIZE];
-  std::snprintf(buf, LOG_BUFFER_SIZE, format_str, 
conditional_conversion(std::forward<Args>(args))...);
-  return std::string(buf);
+inline std::string format_string(int max_size, char const* format_str, 
Args&&... args) {
+  if (0 <= max_size && max_size <= LOG_BUFFER_SIZE) {
+    // use static buffer
+    char buf[LOG_BUFFER_SIZE + 1];
+    std::snprintf(buf, max_size + 1, format_str, 
conditional_conversion(std::forward<Args>(args))...);
+    return std::string(buf);
+  }
+  // use dynamically allocated buffer
+  if (max_size < 0) {
+    // query what buffer size we need
+    int size_needed = std::snprintf(nullptr, 0, format_str, 
conditional_conversion(std::forward<Args>(args))...);
+    if (size_needed < 0) {
+      // error
+      return std::string("Error while formatting log message");
+    }
+    std::vector<char> buffer(size_needed + 1);  // extra '\0' character
+    std::snprintf(buffer.data(), buffer.size(), format_str, 
conditional_conversion(std::forward<Args>(args))...);
+    return std::string(buffer.data());
+  }
+  // use dynamic but fix-sized buffer
+  std::vector<char> buffer(max_size);
+  std::snprintf(buffer.data(), buffer.size(), format_str, 
conditional_conversion(std::forward<Args>(args))...);
+  return std::string(buffer.data());

Review comment:
       changed them to use either the `(const char*, size_t)` or the `(It 
first, It last)` constructors

##########
File path: libminifi/include/core/logging/Logger.h
##########
@@ -68,13 +69,32 @@ inline T conditional_conversion(T t) {
 }
 
 template<typename ... Args>
-inline std::string format_string(char const* format_str, Args&&... args) {
-  char buf[LOG_BUFFER_SIZE];
-  std::snprintf(buf, LOG_BUFFER_SIZE, format_str, 
conditional_conversion(std::forward<Args>(args))...);
-  return std::string(buf);
+inline std::string format_string(int max_size, char const* format_str, 
Args&&... args) {
+  if (0 <= max_size && max_size <= LOG_BUFFER_SIZE) {
+    // use static buffer
+    char buf[LOG_BUFFER_SIZE + 1];
+    std::snprintf(buf, max_size + 1, format_str, 
conditional_conversion(std::forward<Args>(args))...);
+    return std::string(buf);
+  }
+  // use dynamically allocated buffer
+  if (max_size < 0) {
+    // query what buffer size we need
+    int size_needed = std::snprintf(nullptr, 0, format_str, 
conditional_conversion(std::forward<Args>(args))...);

Review comment:
       done




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