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>

benchmark/benchfeatures.cpp

@@ -96,8 +96,14 @@ struct option_struct {
       case 'v':
         verbose = true;
         break;
-      case 'a':
-        simdjson::active_implementation = simdjson::available_implementations[optarg];
+      case 'a': {
+          auto impl = simdjson::available_implementations[optarg];
+          if(impl && impl->supported_by_runtime_system()) {
+            simdjson::active_implementation = impl; 
+          } else { 
+            std::cerr << "implementation " << optarg << " not found or not supported " << std::endl;
+          }
+        } 
         break;
       case 's':
         if (!strcmp(optarg, "stage1")) {

benchmark/minifiercompetition.cpp

@@ -125,9 +125,11 @@ int main(int argc, char *argv[]) {
   size_t outlength;
   uint8_t *cbuffer = (uint8_t *)buffer;
   for (auto imple : simdjson::available_implementations) {
-    BEST_TIME((std::string("simdjson->minify+")+imple->name()).c_str(), (imple->minify(cbuffer, p.size(), cbuffer, outlength) == simdjson::SUCCESS ? outlength : -1),
+    if(imple->supported_by_runtime_system()) {
+      BEST_TIME((std::string("simdjson->minify+")+imple->name()).c_str(), (imple->minify(cbuffer, p.size(), cbuffer, outlength) == simdjson::SUCCESS ? outlength : -1),
             outlength, memcpy(buffer, p.data(), p.size()), repeat, volume,
             !just_data);
+    }
   }
 
   printf("minisize = %zu, original size = %zu  (minified down to %.2f percent "

benchmark/parse.cpp

@@ -67,7 +67,9 @@ void print_usage(ostream& out) {
   out << "-a IMPL      - Use the given parser implementation. By default, detects the most advanced" << endl;
   out << "               implementation supported on the host machine." << endl;
   for (auto impl : simdjson::available_implementations) {
-    out << "-a " << std::left << std::setw(9) << impl->name() << " - Use the " << impl->description() << " parser implementation." << endl;
+    if(impl->supported_by_runtime_system()) {
+      out << "-a " << std::left << std::setw(9) << impl->name() << " - Use the " << impl->description() << " parser implementation." << endl;
+    }
   }
 }
 
@@ -115,11 +117,13 @@ struct option_struct {
         break;
       case 'a': {
         const implementation *impl = simdjson::available_implementations[optarg];
-        if (!impl) {
+        if ((!impl) || (!impl->supported_by_runtime_system())) {
           std::string exit_message = string("Unsupported option value -a ") + optarg + ": expected -a  with one of ";
           for (auto imple : simdjson::available_implementations) {
-            exit_message += imple->name();
-            exit_message += " ";
+            if(imple->supported_by_runtime_system()) {
+              exit_message += imple->name();
+              exit_message += " ";
+            }
           }
           exit_usage(exit_message);
         }

dependencies/cxxopts

@@ -1 +1 @@
-Subproject commit 794c975287355de48158d9a80ed502d26b20a472
+Subproject commit 4b63c333a842295b1bfb79d05863633037328300

doc/implementation-selection.md

@@ -6,6 +6,7 @@ CPU Architecture-Specific Implementations
 * [Inspecting the Detected Implementation](#inspecting-the-detected-implementation)
 * [Querying Available Implementations](#querying-available-implementations)
 * [Manually Selecting the Implementation](#manually-selecting-the-implementation)
+* [Checking that an Implementation can Run on your System](#checking-that-an-implementation-can-run-on-your-system)
 
 Overview
 --------
@@ -70,6 +71,14 @@ And look them up by name:
 ```c++
 cout << simdjson::available_implementations["fallback"]->description() << endl;
 ```
+Though the fallback implementation should always be available, others might be missing. When 
+an implementation is not available, the bracket call `simdjson::available_implementations[name]`
+will return the null pointer.
+
+The available implementations have been compiled but may not necessarily be run safely on your system
+see [Checking that an Implementation can Run on your System](#checking-that-an-implementation-can-run-on-your-system).
+
+
 
 Manually Selecting the Implementation
 -------------------------------------
@@ -81,3 +90,30 @@ can select the CPU architecture yourself:
 // Use the fallback implementation, even though my machine is fast enough for anything
 simdjson::active_implementation = simdjson::available_implementations["fallback"];
 ```
+
+You are responsible for ensuring that the requirements of the selected implementation match your current system.
+Furthermore, you should check that the implementation is available before setting it to `simdjson::active_implementation`
+by comparing it with the null pointer.
+
+```c++
+auto my_implementation = simdjson::available_implementations["haswell"];
+if(! my_implementation) { exit(1); }
+if(! my_implementation->supported_by_runtime_system()) { exit(1); }
+simdjson::active_implementation = my_implementation;
+```
+
+Checking that an Implementation can Run on your System
+-------------------------------------
+
+You should call `supported_by_runtime_system()` to compare the processor's features with the need of the implementation.
+
+```c++
+for (auto implementation : simdjson::available_implementations) {
+  if(implementation->supported_by_runtime_system()) {
+    cout << implementation->name() << ": " << implementation->description() << endl;
+  }
+}
+```
+
+The call to `supported_by_runtime_system()` maybe relatively expensive. Do not call  `supported_by_runtime_system()` each
+time you parse a JSON input (for example). It is meant to be called a handful of times at most in the life of a program.

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;
         }

include/simdjson/implementation.h

@@ -71,6 +71,16 @@ public:
    * @return the name of the implementation, e.g. "haswell", "westmere", "arm64"
    */
   virtual const std::string &description() const { return _description; }
+  
+  /**
+   * The instruction sets this implementation is compiled against
+   * and the current CPU match. This function may poll the current CPU/system
+   * and should therefore not be called too often if performance is a concern.
+   * 
+   *
+   * @return true if the implementation can be safely used on the current system (determined at runtime)
+   */
+  bool supported_by_runtime_system() const;
 
   /**
    * @private For internal implementation use
@@ -180,6 +190,7 @@ public:
    *
    *     const implementation *impl = simdjson::available_implementations["westmere"];
    *     if (!impl) { exit(1); }
+   *     if (!imp->supported_by_runtime_system()) { exit(1); }
    *     simdjson::active_implementation = impl;
    *
    * @param name the implementation to find, e.g. "westmere", "haswell", "arm64"

src/implementation.cpp

@@ -30,6 +30,13 @@ namespace simdjson { namespace internal { const fallback::implementation fallbac
 #endif // SIMDJSON_IMPLEMENTATION_FALLBACK
 
 namespace simdjson {
+
+bool implementation::supported_by_runtime_system() const {
+  uint32_t required_instruction_sets = this->required_instruction_sets();
+  uint32_t supported_instruction_sets = detect_supported_architectures();
+  return ((supported_instruction_sets & required_instruction_sets) == required_instruction_sets);
+}
+
 namespace internal {
 
 /**

tests/basictests.cpp

@@ -1868,6 +1868,10 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "Unsupported architecture value -a %s\n", optarg);
         return EXIT_FAILURE;
       }
+      if(!impl->supported_by_runtime_system()) {
+        fprintf(stderr, "The selected implementation does not match your current CPU: -a %s\n", optarg);
+        return EXIT_FAILURE;
+      }
       simdjson::active_implementation = impl;
       break;
     }

tests/document_stream_tests.cpp

@@ -340,6 +340,10 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "Unsupported architecture value -a %s\n", optarg);
         return EXIT_FAILURE;
       }
+      if(!impl->supported_by_runtime_system()) {
+        fprintf(stderr, "The selected implementation does not match your current CPU: -a %s\n", optarg);
+        return EXIT_FAILURE;
+      }
       simdjson::active_implementation = impl;
       break;
     }

tests/document_tests.cpp

@@ -202,6 +202,10 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "Unsupported architecture value -a %s\n", optarg);
         return EXIT_FAILURE;
       }
+      if(!impl->supported_by_runtime_system()) {
+        fprintf(stderr, "The selected implementation does not match your current CPU: -a %s\n", optarg);
+        return EXIT_FAILURE;
+      }
       simdjson::active_implementation = impl;
       break;
     }

tests/jsoncheck.cpp

@@ -119,6 +119,10 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "Unsupported architecture value -a %s\n", optarg);
         return EXIT_FAILURE;
       }
+      if(!impl->supported_by_runtime_system()) {
+        fprintf(stderr, "The selected implementation does not match your current CPU: -a %s\n", optarg);
+        return EXIT_FAILURE;
+      }
       simdjson::active_implementation = impl;
       break;
     }

tests/minefieldcheck.cpp

@@ -117,6 +117,10 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "Unsupported architecture value -a %s\n", optarg);
         return EXIT_FAILURE;
       }
+      if(!impl->supported_by_runtime_system()) {
+        fprintf(stderr, "The selected implementation does not match your current CPU: -a %s\n", optarg);
+        return EXIT_FAILURE;
+      }
       simdjson::active_implementation = impl;
       break;
     }

tests/readme_examples.cpp

@@ -201,10 +201,24 @@ void implementation_selection_2() {
   }
 }
 
+void implementation_selection_2_safe() {
+  for (auto implementation : simdjson::available_implementations) {
+    if(implementation->supported_by_runtime_system()) {
+      cout << implementation->name() << ": " << implementation->description() << endl;
+    }
+  }
+}
 void implementation_selection_3() {
   cout << simdjson::available_implementations["fallback"]->description() << endl;
 }
 
+void implementation_selection_safe() {
+  auto my_implementation = simdjson::available_implementations["haswell"];
+  if(! my_implementation) { exit(1); }
+  if(! my_implementation->supported_by_runtime_system()) { exit(1); }
+  simdjson::active_implementation = my_implementation;
+}
+
 void implementation_selection_4() {
   // Use the fallback implementation, even though my machine is fast enough for anything
   simdjson::active_implementation = simdjson::available_implementations["fallback"];

tools/json2json.cpp

@@ -9,7 +9,11 @@ SIMDJSON_PUSH_DISABLE_ALL_WARNINGS
 #include "cxxopts.hpp"
 SIMDJSON_POP_DISABLE_WARNINGS
 
+#if CXXOPTS__VERSION_MAJOR < 3 
 int main(int argc, char *argv[]) {
+#else
+int main(int argc, const char *argv[]) {
+#endif
 #ifdef __cpp_exceptions
   try {
 #endif

tools/jsonstats.cpp

@@ -188,8 +188,11 @@ stat_t simdjson_compute_stats(const simdjson::padded_string &p) {
   recurse(doc, s, 0);
   return s;
 }
-
+#if CXXOPTS__VERSION_MAJOR < 3 
 int main(int argc, char *argv[]) {
+#else
+int main(int argc, const char *argv[]) {
+#endif
 #ifdef __cpp_exceptions
   try {
 #endif

tools/minify.cpp

@@ -20,7 +20,11 @@ void usage(std::string message) {
   std::cerr << options.help() << std::endl;
 }
 
+#if CXXOPTS__VERSION_MAJOR < 3 
 int main(int argc, char *argv[]) {
+#else
+int main(int argc, const char *argv[]) {
+#endif
 #ifdef __cpp_exceptions
   try {
 #endif
@@ -28,7 +32,9 @@ int main(int argc, char *argv[]) {
   ss << "Parser implementation (by default, detects the most advanced implementation supported on the host machine)."  << std::endl;
   ss << "Available parser implementations:" << std::endl;
   for (auto impl : simdjson::available_implementations) {
-    ss << "-a " << std::left << std::setw(9) << impl->name() << " - Use the " << impl->description() << " parser implementation." << std::endl;
+    if(impl->supported_by_runtime_system()) {
+      ss << "-a " << std::left << std::setw(9) << impl->name() << " - Use the " << impl->description() << " parser implementation." << std::endl;
+    }
   }
   options.add_options()
     ("a,arch", ss.str(), cxxopts::value<std::string>())
@@ -54,6 +60,10 @@ int main(int argc, char *argv[]) {
       usage("Unsupported implementation.");
       return EXIT_FAILURE;
     }
+    if(!impl->supported_by_runtime_system()) {
+      usage("The selected implementation does not match your current CPU.");
+      return EXIT_FAILURE;
+    }
     simdjson::active_implementation = impl;
   }