add an example gtest case, useful for unit-testing compiler pass

frontends/p4/p4-parse.h

@@ -1,5 +1,5 @@
 /*
-Copyright 2013-present Barefoot Networks, Inc. 
+Copyright 2013-present Barefoot Networks, Inc.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -23,5 +23,6 @@ limitations under the License.
 namespace IR { class Global; }
 
 const IR::P4Program *parse_P4_16_file(const char *name, FILE *in);
+const IR::P4Program *parse_string(std::string &pgm);
 
 #endif /* _P4_P4_PARSE_H_ */

frontends/p4/p4-parse.ypp

@@ -993,6 +993,18 @@ const IR::P4Program *parse_P4_16_file(const char *name, FILE *in) {
     return new IR::P4Program(declarations->srcInfo, declarations);
 }
 
+const IR::P4Program *parse_string(const std::string &pgm) {
+    int errors = 0;
+    declarations = new IR::IndexedVector<IR::Node>();
+    YY_BUFFER_STATE state = yy_scan_string(pgm.c_str());
+    errors |= yyparse();
+    yy_delete_buffer(state);
+    if (errors) {
+        return nullptr;
+    }
+    return new IR::P4Program(declarations->srcInfo, declarations);
+}
+
 // check that right shift >>
 // has the two tokens at consecutive positions
 // (not separated by anything else)

test/gtest/Makefile.am

@@ -15,7 +15,8 @@
 # General GTest unit tests. Add tests here if they don't have a logical home
 # elsewhere in the codebase.
 gtest_unittest_UNIFIED = \
-	test/gtest/opeq_test.cpp
+	test/gtest/opeq_test.cpp \
+	test/gtest/typecheck_test.cpp
 
 cpplint_FILES += $(gtest_unittest_UNIFIED)
 gtest_SOURCES += $(gtest_unittest_SOURCES)

test/gtest/helper.h

@@ -0,0 +1,51 @@
+/*
+Copyright 2013-present Barefoot Networks, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include <string>
+
+/* preprocessing by prepending the content of core.p4 to test program */
+std::string with_core_p4 (std::string pgm) {
+    const std::string core_p4 = " \
+error { \
+    NoError, \
+    PacketTooShort, \
+    NoMatch, \
+    StackOutOfBounds, \
+    OverwritingHeader, \
+    HeaderTooShort, \
+    ParserTimeout \
+} \
+extern packet_in { \
+    void extract<T>(out T hdr); \
+    void extract<T>(out T variableSizeHeader, \
+                    in bit<32> variableFieldSizeInBits); \
+    T lookahead<T>(); \
+    void advance(in bit<32> sizeInBits); \
+    bit<32> length(); \
+} \
+extern packet_out { \
+    void emit<T>(in T hdr); \
+    void emit<T>(in bool condition, in T data); \
+} \
+@name(\"NoAction\") \
+action NoAction() {} \
+match_kind { \
+    exact, \
+    ternary, \
+    lpm \
+} \n";
+    return core_p4 + pgm;
+}

test/gtest/typecheck_test.cpp

@@ -0,0 +1,62 @@
+/*
+Copyright 2013-present Barefoot Networks, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include "gtest/gtest.h"
+
+#include "ir/ir.h"
+#include "p4/p4-parse.h"
+#include "p4/createBuiltins.h"
+#include "frontends/p4/typeMap.h"
+#include "frontends/common/constantFolding.h"
+#include "frontends/p4/typeChecking/bindVariables.h"
+#include "frontends/common/resolveReferences/resolveReferences.h"
+
+#include "p4/validateParsedProgram.h"
+#include "p4/createBuiltins.h"
+#include "p4/unusedDeclarations.h"
+#include "p4/typeChecking/typeChecker.h"
+
+#include "helper.h"
+
+using namespace P4;
+
+TEST(UNITTEST, helloworld) {
+
+    std::string program = with_core_p4(
+        "parser Parser<H, M> (packet_in p){ state start{} };\n"
+        "control empty() { apply {} };\n"
+        "package top(empty e);\n"
+        "top(empty()) main;\n");
+
+    const IR::P4Program* pgm = parse_string(program);
+    ASSERT_TRUE(pgm != nullptr);
+
+    ReferenceMap  refMap;
+    TypeMap       typeMap;
+
+    PassManager passes = {
+      new ValidateParsedProgram(false),
+      new CreateBuiltins(),
+      new ResolveReferences(&refMap, true),
+      new ConstantFolding(&refMap, nullptr),
+      new ResolveReferences(&refMap),
+//      new TypeInference(&refMap, &typeMap),
+    };
+
+    pgm = pgm->apply(passes);
+
+    ASSERT_TRUE(pgm != nullptr);
+}