diff --git a/Doxyfile b/Doxyfile
index 83b7e4e37..0d31423b9 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -28,7 +28,6 @@ INHERIT_DOCS           = YES
 SEPARATE_MEMBER_PAGES  = NO
 TAB_SIZE               = 4
 ALIASES                =
-TCL_SUBST              =
 OPTIMIZE_OUTPUT_FOR_C  = NO
 OPTIMIZE_OUTPUT_JAVA   = NO
 OPTIMIZE_FOR_FORTRAN   = NO
@@ -137,7 +136,6 @@ CLANG_OPTIONS          =
 # Configuration options related to the alphabetical class index
 #---------------------------------------------------------------------------
 ALPHABETICAL_INDEX     = YES
-COLS_IN_ALPHA_INDEX    = 5
 IGNORE_PREFIX          =
 #---------------------------------------------------------------------------
 # Configuration options related to the HTML output
@@ -278,12 +276,10 @@ GENERATE_TAGFILE       =
 ALLEXTERNALS           = NO
 EXTERNAL_GROUPS        = YES
 EXTERNAL_PAGES         = YES
-PERL_PATH              = /usr/bin/perl
 #---------------------------------------------------------------------------
 # Configuration options related to the dot tool
 #---------------------------------------------------------------------------
 CLASS_DIAGRAMS         = NO
-MSCGEN_PATH            =
 DIA_PATH               =
 HIDE_UNDOC_RELATIONS   = YES
 HAVE_DOT               = NO
diff --git a/circle.yml b/circle.yml
index 043f8848f..ecdcae6b1 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,6 +1,20 @@
 version: 2.1
 
+executors:
+  linux-gcc-latest:
+    docker:
+      - image: ethereum/cpp-build-env:16-gcc-10
+  linux-clang-latest:
+    docker:
+      - image: ethereum/cpp-build-env:16-clang-11
+
+
 commands:
+  install_doxygen:
+    steps:
+      - run:
+          name: "Install doxygen"
+          command: sudo apt-get -q update && sudo apt-get -qy install doxygen
   build:
     parameters:
       build_type:
@@ -70,8 +84,7 @@ commands:
 jobs:
 
   lint:
-    docker:
-      - image: ethereum/cpp-build-env:12-lint
+    executor: linux-clang-latest
     steps:
     - checkout
     - run:
@@ -92,6 +105,7 @@ jobs:
           bumpversion --dry-run --verbose major
           bumpversion --dry-run --verbose minor
           bumpversion --dry-run --verbose patch
+    - install_doxygen
     - run:
         name: "Test documentation"
         command: |
@@ -107,10 +121,10 @@ jobs:
         destination: docs
 
   upload-docs:
-    docker:
-      - image: ethereum/cpp-build-env:12-lint
+    executor: linux-clang-latest
     steps:
       - checkout
+      - install_doxygen
       - run:
           name: "Generate documentation"
           command: doxygen Doxyfile
@@ -123,9 +137,8 @@ jobs:
             git commit -m "Update docs"
             git push -f "https://$GITHUB_TOKEN@github.com/ethereum/evmc.git" HEAD:gh-pages
 
-  build-clang10-coverage:
-    docker:
-      - image: ethereum/cpp-build-env:14-clang-10
+  build-clang-coverage:
+    executor: linux-clang-latest
     steps:
       - checkout
       - build:
@@ -157,31 +170,27 @@ jobs:
             codecov --file ~/build/evmc.lcov -X gcov
 
 
-  build-gcc8-cxx17:
+  build-gcc8:
     docker:
       - image: ethereum/cpp-build-env:12-gcc-8
-    environment:
-      CMAKE_OPTIONS: -DCMAKE_CXX_STANDARD=17
     steps:
       - checkout
       - build
       - test
 
-  build-gcc10-cxx17-sanitizers:
-    docker:
-      - image: ethereum/cpp-build-env:14-gcc-10
+  build-gcc-sanitizers:
+    executor: linux-gcc-latest
     environment:
-      CMAKE_OPTIONS: -DCMAKE_CXX_STANDARD=17 -DSANITIZE=address,undefined
+      CMAKE_OPTIONS: -DSANITIZE=address,undefined
     steps:
       - checkout
       - build
       - test
 
-  build-clang10-cxx17-sanitizers:
-    docker:
-      - image: ethereum/cpp-build-env:14-clang-10
+  build-clang-sanitizers:
+    executor: linux-clang-latest
     environment:
-      CMAKE_OPTIONS: -DCMAKE_CXX_STANDARD=17 -DSANITIZE=address,undefined,nullability,implicit-unsigned-integer-truncation,implicit-signed-integer-truncation
+      CMAKE_OPTIONS: -DSANITIZE=address,undefined,nullability,implicit-unsigned-integer-truncation,implicit-signed-integer-truncation
       UBSAN_OPTIONS: halt_on_error=1
     steps:
       - checkout
@@ -374,10 +383,10 @@ workflows:
   evmc:
     jobs:
       - lint
-      - build-clang10-coverage
-      - build-gcc8-cxx17
-      - build-gcc10-cxx17-sanitizers
-      - build-clang10-cxx17-sanitizers
+      - build-clang-coverage
+      - build-gcc8
+      - build-gcc-sanitizers
+      - build-clang-sanitizers
       - build-clang9-asan
       - build-gcc-min
       - build-clang-min
@@ -394,7 +403,7 @@ workflows:
       - bindings-java
       - bindings-rust:
           requires:
-            - build-gcc8-cxx17
+            - build-gcc8
       - bindings-rust-asan:
           requires:
             - build-clang9-asan
diff --git a/examples/example_host.cpp b/examples/example_host.cpp
index 90316eaf9..b35e73727 100644
--- a/examples/example_host.cpp
+++ b/examples/example_host.cpp
@@ -60,8 +60,8 @@ class ExampleHost : public evmc::Host
         return accounts.find(addr) != accounts.end();
     }
 
-    evmc::bytes32 get_storage(const evmc::address& addr, const evmc::bytes32& key) const
-        noexcept final
+    evmc::bytes32 get_storage(const evmc::address& addr,
+                              const evmc::bytes32& key) const noexcept final
     {
         const auto account_iter = accounts.find(addr);
         if (account_iter == accounts.end())
diff --git a/include/evmc/evmc.hpp b/include/evmc/evmc.hpp
index 6d0bac9f2..6df50197a 100644
--- a/include/evmc/evmc.hpp
+++ b/include/evmc/evmc.hpp
@@ -272,7 +272,8 @@ namespace internal
 constexpr int from_hex(char c) noexcept
 {
     return (c >= 'a' && c <= 'f') ? c - ('a' - 10) :
-                                    (c >= 'A' && c <= 'F') ? c - ('A' - 10) : c - '0';
+           (c >= 'A' && c <= 'F') ? c - ('A' - 10) :
+                                    c - '0';
 }
 
 constexpr uint8_t byte(const char* s, size_t i) noexcept