From 72d3f4896a46a9b820fbb6955d738fac0f31b371 Mon Sep 17 00:00:00 2001
From: Kai Aoki <kai.aoki@sigboost.audio>
Date: Tue, 12 Jul 2022 00:10:57 +0900
Subject: [PATCH 1/4] Update httplib.h

use std::exception_ptr
---
 httplib.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/httplib.h b/httplib.h
index 1c4db98..111276a 100644
--- a/httplib.h
+++ b/httplib.h
@@ -616,7 +616,7 @@ public:
   using Handler = std::function<void(const Request &, Response &)>;
 
   using ExceptionHandler =
-      std::function<void(const Request &, Response &, std::exception &e)>;
+      std::function<void(const Request &, Response &, std::exception_ptr &ep)>;
 
   enum class HandlerResponse {
     Handled,
@@ -5733,7 +5733,8 @@ Server::process_request(Stream &strm, bool close_connection,
     routed = routing(req, res, strm);
   } catch (std::exception &e) {
     if (exception_handler_) {
-      exception_handler_(req, res, e);
+      auto ep = std::current_exception();
+      exception_handler_(req, res, ep);
       routed = true;
     } else {
       res.status = 500;

From d4ab2fa0e6a1f903a5f4be761d1f1ed5e4aaee8c Mon Sep 17 00:00:00 2001
From: Kai Aoki <kai.aoki@sigboost.audio>
Date: Fri, 15 Jul 2022 01:45:10 +0900
Subject: [PATCH 2/4] fix double ref and case of exceptions that are not
 std::exception

---
 httplib.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/httplib.h b/httplib.h
index 111276a..7647fed 100644
--- a/httplib.h
+++ b/httplib.h
@@ -616,7 +616,7 @@ public:
   using Handler = std::function<void(const Request &, Response &)>;
 
   using ExceptionHandler =
-      std::function<void(const Request &, Response &, std::exception_ptr &ep)>;
+      std::function<void(const Request &, Response &, std::exception_ptr ep)>;
 
   enum class HandlerResponse {
     Handled,
@@ -5741,8 +5741,14 @@ Server::process_request(Stream &strm, bool close_connection,
       res.set_header("EXCEPTION_WHAT", e.what());
     }
   } catch (...) {
-    res.status = 500;
-    res.set_header("EXCEPTION_WHAT", "UNKNOWN");
+    if (exception_handler_) {
+      auto ep = std::current_exception();
+      exception_handler_(req, res, ep);
+      routed = true;
+    } else {
+      res.status = 500;
+      res.set_header("EXCEPTION_WHAT", "UNKNOWN");
+    }
   }
 #endif
 

From 869f5bb2794c0c2fb458fae898e20c0f179ffc88 Mon Sep 17 00:00:00 2001
From: Kai Aoki <kai.aoki@sigboost.audio>
Date: Fri, 15 Jul 2022 11:50:26 +0900
Subject: [PATCH 3/4] fix ExceptionHandlerTest.ContentLength

---
 test/test.cc | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/test/test.cc b/test/test.cc
index 3f94e58..6bd3330 100644
--- a/test/test.cc
+++ b/test/test.cc
@@ -1249,8 +1249,13 @@ TEST(ExceptionHandlerTest, ContentLength) {
   Server svr;
 
   svr.set_exception_handler([](const Request & /*req*/, Response &res,
-                               std::exception &e) {
-    EXPECT_EQ("abc", std::string(e.what()));
+                               std::exception_ptr ep) {
+    EXPECT_FALSE(ep == nullptr);
+    try{
+      std::rethrow_exception(ep);
+    }catch(std::exception& e){
+      EXPECT_EQ("abc", std::string(e.what()));
+    }
     res.status = 500;
     res.set_content("abcdefghijklmnopqrstuvwxyz",
                     "text/html"); // <= Content-Length still 13 at this point

From 07e614eef7c88daa734e5d32e050f1e7138a99db Mon Sep 17 00:00:00 2001
From: yhirose <yuji.hirose.bug@gmail.com>
Date: Fri, 15 Jul 2022 17:32:38 -0400
Subject: [PATCH 4/4] clangformat and README update

---
 README.md    | 14 +++++++++++---
 test/test.cc |  6 ++----
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 48eb423..36acd2a 100644
--- a/README.md
+++ b/README.md
@@ -212,15 +212,23 @@ svr.set_error_handler([](const auto& req, auto& res) {
 The exception handler gets called if a user routing handler throws an error.
 
 ```cpp
-svr.set_exception_handler([](const auto& req, auto& res, std::exception &e) {
-  res.status = 500;
+svr.set_exception_handler([](const auto& req, auto& res, std::exception_ptr ep) {
   auto fmt = "<h1>Error 500</h1><p>%s</p>";
   char buf[BUFSIZ];
-  snprintf(buf, sizeof(buf), fmt, e.what());
+  try {
+    std::rethrow_exception(ep);
+  } catch (std::exception &e) {
+    snprintf(buf, sizeof(buf), fmt, e.what());
+  } catch (...) { // See the following NOTE
+    snprintf(buf, sizeof(buf), fmt, "Unknown Exception");
+  }
   res.set_content(buf, "text/html");
+  res.status = 500;
 });
 ```
 
+NOTE: if you don't provide the `catch (...)` block for a rethrown exception pointer, an uncaught exception will end up causing the server crash. Be careful!
+
 ### Pre routing handler
 
 ```cpp
diff --git a/test/test.cc b/test/test.cc
index 58dc5b2..6ca8497 100644
--- a/test/test.cc
+++ b/test/test.cc
@@ -1251,11 +1251,9 @@ TEST(ExceptionHandlerTest, ContentLength) {
   svr.set_exception_handler([](const Request & /*req*/, Response &res,
                                std::exception_ptr ep) {
     EXPECT_FALSE(ep == nullptr);
-    try{
+    try {
       std::rethrow_exception(ep);
-    }catch(std::exception& e){
-      EXPECT_EQ("abc", std::string(e.what()));
-    }
+    } catch (std::exception &e) { EXPECT_EQ("abc", std::string(e.what())); }
     res.status = 500;
     res.set_content("abcdefghijklmnopqrstuvwxyz",
                     "text/html"); // <= Content-Length still 13 at this point