Make it possible to check that an implementation is supported at runtime (#1197)

* Make it possible to check that an implementation is supported at runtime.

* add CI fuzzing on arm 64 bit

This adds fuzzing on drone.io arm64

For some reason, leak detection had to be disabled. If it is enabled, the fuzzer falsely reports a crash at the end of fuzzing.

Closes: #1188

* Guarding the implementation accesses.

* Better doc.

* Updating cxxopts.

* Make it possible to check that an implementation is supported at runtime.

* Guarding the implementation accesses.

* Better doc.

* Updating cxxopts.

* We need to accomodate cxxopts

Co-authored-by: Paul Dreik <github@pauldreik.se>

fuzz/fuzz_implementations.cpp

@@ -67,7 +67,13 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
     // make this dynamic, so it works regardless of how it was compiled
     // or what hardware it runs on
     constexpr std::size_t Nimplementations_max=3;
-    const std::size_t Nimplementations=simdjson::available_implementations.size();
+    std::size_t Nimplementations = 0;
+    
+    for(auto impl : simdjson::available_implementations) {
+        if(impl->supported_by_runtime_system()) {
+              Nimplementations++;
+        }
+    }
     if(Nimplementations>Nimplementations_max) {
         //there is another backend added, please bump Nimplementations_max!
         std::abort();
@@ -78,7 +84,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
     {
         std::size_t i=0;
         for(auto& e: simdjson::available_implementations) {
-            implementations[i++].impl=e;
+            if(e->supported_by_runtime_system()) {
+              implementations[i++].impl=e;
+            }
         }
     }
 

fuzz/fuzz_minifyimpl.cpp

@@ -32,16 +32,19 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
     };
 
 
-    auto first=simdjson::available_implementations.begin();
-    auto last=simdjson::available_implementations.end();
+    auto const first = simdjson::available_implementations.begin();
+    auto const last = simdjson::available_implementations.end();
 
-    //make sure there is an implementation
-    assert(first!=last);
+
+    auto it = first;
+    while((it != last) && (!(*it)->supported_by_runtime_system())) { it++; }
+    assert(it != last);
 
     const auto reference=minify(*first);
 
     bool failed=false;
-    for(auto it=first+1;it!=last; ++it) {
+    for(;it != last; ++it) {
+        if(!(*it)->supported_by_runtime_system()) { continue; }
         const auto current=minify(*it);
         if(current!=reference) {
             failed=true;
@@ -50,7 +53,8 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
 
     if(failed) {
         std::cerr<<std::boolalpha<<"Mismatch between implementations of minify() found:\n";
-        for(auto it=first;it!=last; ++it) {
+        for(it = first;it != last; ++it) {
+            if(!(*it)->supported_by_runtime_system()) { continue; }
             const auto current=minify(*it);
             std::string tmp(current.begin(),current.end());
             std::cerr<<(*it)->name()<<" returns "<<tmp<<std::endl;

fuzz/fuzz_utf8.cpp

@@ -18,16 +18,20 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
     };
 
 
-    auto first=simdjson::available_implementations.begin();
-    auto last=simdjson::available_implementations.end();
+    auto first = simdjson::available_implementations.begin();
+    auto last = simdjson::available_implementations.end();
 
-    //make sure there is an implementation
-    assert(first!=last);
 
-    const bool reference=utf8verify(*first);
+    auto it = first;
+    while((it != last) && (!(*it)->supported_by_runtime_system())) { it++; }
+    assert(it != last);
+
+
+    const bool reference=utf8verify(*it);
 
     bool failed=false;
-    for(auto it=first+1;it!=last; ++it) {
+    for(; it != last; ++it) {
+        if(!(*it)->supported_by_runtime_system()) { continue; }
         const bool current=utf8verify(*it);
         if(current!=reference) {
             failed=true;
@@ -36,7 +40,8 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
 
     if(failed) {
         std::cerr<<std::boolalpha<<"Mismatch between implementations of validate_utf8() found:\n";
-        for(auto it=first;it!=last; ++it) {
+        for(it = first;it != last; ++it) {
+            if(!(*it)->supported_by_runtime_system()) { continue; }
             const bool current=utf8verify(*it);
             std::cerr<<(*it)->name()<<" returns "<<current<<std::endl;
         }