From c7a7d16992e30d60e50634b55ca8b524ba2d971c Mon Sep 17 00:00:00 2001
From: Damian Jarek <damian.jarek93@gmail.com>
Date: Fri, 1 Mar 2019 22:55:58 +0100
Subject: [PATCH] Allow the use of string_body and vector_body with
 -fno-exceptions

`string_body` and `vector_body` will no longer translate all exceptions
to "buffer_overflow" error code. `buffer_overflow` error can now only
occur if the Body's max_size() is exceeded.

Changes required:
Code that relies on exceptions thrown from value_type's reserve/resize
being translated into an error code must implement a mechanism to catch
the exception.

Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>
---
 include/boost/beast/http/string_body.hpp | 22 ++++++----------------
 include/boost/beast/http/vector_body.hpp | 22 ++++++----------------
 2 files changed, 12 insertions(+), 32 deletions(-)

diff --git a/include/boost/beast/http/string_body.hpp b/include/boost/beast/http/string_body.hpp
index 6c813dd9..121a718a 100644
--- a/include/boost/beast/http/string_body.hpp
+++ b/include/boost/beast/http/string_body.hpp
@@ -15,6 +15,7 @@
 #include <boost/beast/http/error.hpp>
 #include <boost/beast/http/message.hpp>
 #include <boost/beast/core/buffers_range.hpp>
+#include <boost/beast/core/detail/clamp.hpp>
 #include <boost/beast/core/detail/type_traits.hpp>
 #include <boost/asio/buffer.hpp>
 #include <boost/optional.hpp>
@@ -94,21 +95,12 @@ public:
         {
             if(length)
             {
-                if(static_cast<std::size_t>(*length) != *length)
-                {
-                    ec = error::buffer_overflow;
-                    return;
-                }
-                try
-                {
-                    body_.reserve(
-                        static_cast<std::size_t>(*length));
-                }
-                catch(std::exception const&)
+                if(*length > body_.max_size())
                 {
                     ec = error::buffer_overflow;
                     return;
                 }
+                body_.reserve(beast::detail::clamp(*length));
             }
             ec = {};
         }
@@ -120,15 +112,13 @@ public:
         {
             auto const extra = buffer_size(buffers);
             auto const size = body_.size();
-            try
-            {
-                body_.resize(size + extra);
-            }
-            catch(std::exception const&)
+            if (extra > body_.max_size() - size)
             {
                 ec = error::buffer_overflow;
                 return 0;
             }
+
+            body_.resize(size + extra);
             ec = {};
             CharT* dest = &body_[size];
             for(auto b : beast::buffers_range_ref(buffers))
diff --git a/include/boost/beast/http/vector_body.hpp b/include/boost/beast/http/vector_body.hpp
index 76195c29..78cf637f 100644
--- a/include/boost/beast/http/vector_body.hpp
+++ b/include/boost/beast/http/vector_body.hpp
@@ -14,6 +14,7 @@
 #include <boost/beast/core/buffer_size.hpp>
 #include <boost/beast/http/error.hpp>
 #include <boost/beast/http/message.hpp>
+#include <boost/beast/core/detail/clamp.hpp>
 #include <boost/beast/core/detail/type_traits.hpp>
 #include <boost/asio/buffer.hpp>
 #include <boost/optional.hpp>
@@ -88,21 +89,12 @@ public:
         {
             if(length)
             {
-                if(static_cast<std::size_t>(*length) != *length)
-                {
-                    ec = error::buffer_overflow;
-                    return;
-                }
-                try
-                {
-                    body_.reserve(
-                        static_cast<std::size_t>(*length));
-                }
-                catch(std::exception const&)
+                if(*length > body_.max_size())
                 {
                     ec = error::buffer_overflow;
                     return;
                 }
+                body_.reserve(beast::detail::clamp(*length));
             }
             ec = {};
         }
@@ -114,15 +106,13 @@ public:
         {
             auto const n = buffer_size(buffers);
             auto const len = body_.size();
-            try
-            {
-                body_.resize(len + n);
-            }
-            catch(std::exception const&)
+            if (n > body_.max_size() - len)
             {
                 ec = error::buffer_overflow;
                 return 0;
             }
+
+            body_.resize(len + n);
             ec = {};
             return net::buffer_copy(net::buffer(
                 &body_[0] + len, n), buffers);