diff --git a/backward.hpp b/backward.hpp
index 19d5ba3..491f6bb 100644
--- a/backward.hpp
+++ b/backward.hpp
@@ -3918,7 +3918,6 @@ class cfile_streambuf : public std::streambuf {
 
 private:
   FILE *sink;
-  std::vector<char> buffer;
 };
 
 #ifdef BACKWARD_SYSTEM_LINUX
@@ -4162,16 +4161,15 @@ class SignalHandling {
                                 sizeof posix_signals / sizeof posix_signals[0]);
   }
 
-  SignalHandling(const std::vector<int> &posix_signals = make_default_signals())
-      : _loaded(false) {
+  static bool installHandler(const std::vector<int> &posix_signals,
+                             void (*handler)(int, siginfo_t *, void *),
+                             char *altstack, size_t altstack_size) {
     bool success = true;
 
-    const size_t stack_size = 1024 * 1024 * 8;
-    _stack_content.reset(static_cast<char *>(malloc(stack_size)));
-    if (_stack_content) {
+    if (altstack) {
       stack_t ss;
-      ss.ss_sp = _stack_content.get();
-      ss.ss_size = stack_size;
+      ss.ss_sp = altstack;
+      ss.ss_size = altstack_size;
       ss.ss_flags = 0;
       if (sigaltstack(&ss, nullptr) < 0) {
         success = false;
@@ -4191,7 +4189,7 @@ class SignalHandling {
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdisabled-macro-expansion"
 #endif
-      action.sa_sigaction = &sig_handler;
+      action.sa_sigaction = handler;
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #endif
@@ -4201,9 +4199,21 @@ class SignalHandling {
         success = false;
     }
 
-    _loaded = success;
+    return success;
   }
 
+  SignalHandling(const std::vector<int> &posix_signals,
+                 void (*handler)(int, siginfo_t *, void *))
+    : _loaded(false) {
+    const size_t stack_size = 1024 * 1024 * 8;
+    _stack_content.reset(static_cast<char *>(malloc(stack_size)));
+    _loaded = installHandler(posix_signals, handler, _stack_content.get(),
+                             stack_size);
+  }
+
+  SignalHandling(const std::vector<int> &posix_signals = make_default_signals())
+      : SignalHandling(posix_signals, sig_handler) {}
+
   bool loaded() const { return _loaded; }
 
   static void handleSignal(int, siginfo_t *info, void *_ctx) {
@@ -4249,7 +4259,7 @@ class SignalHandling {
 
     Printer printer;
     printer.address = true;
-    printer.print(st, stderr);
+    fflush(printer.print(st, stderr));
 
 #if (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 700) || \
     (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200809L)
@@ -4449,7 +4459,7 @@ class SignalHandling {
     st.skip_n_firsts(skip_frames);
 
     printer.address = true;
-    printer.print(st, std::cerr);
+    printer.print(st, std::cerr) << std::flush;
   }
 };