Merge pull request #383 from ethereum/example-dynamic

examples: extend example to support dynamic loading

circle.yml

@@ -30,7 +30,10 @@ commands:
           name: "Test"
           command: |
             cmake --build ~/build --target test -- ARGS="-j4 --schedule-random --output-on-failure"
-            ~/build/examples/evmc-example
+            # Test statically linked end-to-end example
+            ~/build/examples/evmc-example-static
+            # Test dynamically loaded end-to-end example
+            ~/build/examples/evmc-example ~/build/examples/example_vm/libevmc-example-vm.so
       - run:
           name: "Install"
           command: cmake --build ~/build --target install

examples/CMakeLists.txt

@@ -16,5 +16,9 @@ add_subdirectory(example_precompiles_vm)
 add_library(evmc-example-host STATIC example_host.cpp)
 target_link_libraries(evmc-example-host PRIVATE evmc)
 
+add_executable(evmc-example-static example.c)
+target_link_libraries(evmc-example-static PRIVATE evmc-example-host evmc-example-vm-static evmc)
+target_compile_definitions(evmc-example-static PRIVATE STATICALLY_LINKED_EXAMPLE)
+
 add_executable(evmc-example example.c)
-target_link_libraries(evmc-example PRIVATE evmc-example-host evmc-example-vm-static evmc)
+target_link_libraries(evmc-example PRIVATE evmc-example-host evmc evmc::loader)

examples/example.c

@@ -4,18 +4,37 @@
  */
 
 #include "example_host.h"
+#ifdef STATICALLY_LINKED_EXAMPLE
 #include "example_vm/example_vm.h"
+#endif
 
 #include <evmc/helpers.h>
+#include <evmc/loader.h>
 
 #include <inttypes.h>
 #include <stdio.h>
 
-int main()
+int main(int argc, char* argv[])
 {
+#ifdef STATICALLY_LINKED_EXAMPLE
+    (void)argc;
+    (void)argv;
     struct evmc_instance* vm = evmc_create_example_vm();
+    if (!vm)
+        return EVMC_LOADER_INSTANCE_CREATION_FAILURE;
     if (!evmc_is_abi_compatible(vm))
-        return -1;
+        return EVMC_LOADER_ABI_VERSION_MISMATCH;
+#else
+    const char* config_string = (argc > 1) ? argv[1] : "example-vm.so";
+    enum evmc_loader_error_code error_code;
+    struct evmc_instance* vm = evmc_load_and_configure(config_string, &error_code);
+    if (!vm)
+    {
+        printf("Loading error: %d\n", error_code);
+        // NOTE: the values are small enough for casting
+        return (int)error_code;
+    }
+#endif
 
     // EVM bytecode goes here. This is one of the examples.
     const uint8_t code[] = "\x30\x60\x00\x52\x59\x60\x00\xf3";