[llvm-c] Added a C-API binding to query the LLVM version

The LLVM C bindings currently offer no way to query the version string
dynamically. This is a useful feature in situations where a program
isn't compiled against a specific version of LLVM but rather loads it
dynamically (e.g. using dlopen()).

In situations where the shared library filename doesn't reveal the
version (e.g. LLVM-C.dll) and to adapt to version-specific API
differences, it is then useful to be able to query the version string by
calling the proposed LLVMGetVersion function.

Differential Revision: https://reviews.llvm.org/D139381

llvm/include/llvm-c/Core.h

@@ -479,6 +479,16 @@ void LLVMInitializeCore(LLVMPassRegistryRef R);
     @see ManagedStatic */
 void LLVMShutdown(void);
 
+/*===-- Version query -----------------------------------------------------===*/
+
+/**
+ * Return the major, minor, and patch version of LLVM
+ *
+ * The version components are returned via the function's three output
+ * parameters or skipped if a NULL pointer was supplied.
+ */
+void LLVMGetVersion(unsigned *Major, unsigned *Minor, unsigned *Patch);
+
 /*===-- Error handling ----------------------------------------------------===*/
 
 char *LLVMCreateMessage(const char *Message);

llvm/lib/IR/Core.cpp

@@ -61,6 +61,17 @@ void LLVMShutdown() {
   llvm_shutdown();
 }
 
+/*===-- Version query -----------------------------------------------------===*/
+
+void LLVMGetVersion(unsigned *Major, unsigned *Minor, unsigned *Patch) {
+    if (Major)
+        *Major = LLVM_VERSION_MAJOR;
+    if (Minor)
+        *Minor = LLVM_VERSION_MINOR;
+    if (Patch)
+        *Patch = LLVM_VERSION_PATCH;
+}
+
 /*===-- Error handling ----------------------------------------------------===*/
 
 char *LLVMCreateMessage(const char *Message) {

llvm/unittests/IR/CMakeLists.txt

@@ -46,6 +46,7 @@ add_llvm_unittest(IRTests
   VectorTypesTest.cpp
   VerifierTest.cpp
   VPIntrinsicTest.cpp
+  CoreBindings.cpp
   )
 
 target_link_libraries(IRTests PRIVATE LLVMTestingSupport)

llvm/unittests/IR/CoreBindings.cpp

@@ -0,0 +1,26 @@
+//===- llvm/unittest/IR/CoreBindings.cpp - Tests for C-API bindings -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-c/Core.h"
+#include "llvm/Config/llvm-config.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+TEST(CoreBindings, VersionTest) {
+  // Test ability to ignore output parameters
+  LLVMGetVersion(nullptr, nullptr, nullptr);
+
+  unsigned Major, Minor, Patch;
+  LLVMGetVersion(&Major, &Minor, &Patch);
+  EXPECT_EQ(Major, (unsigned)LLVM_VERSION_MAJOR);
+  EXPECT_EQ(Minor, (unsigned)LLVM_VERSION_MINOR);
+  EXPECT_EQ(Patch, (unsigned)LLVM_VERSION_PATCH);
+}
+
+} // end anonymous namespace