Added a C-API binding to query the LLVM version

[wjakob]

Summary

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.

[wjakob]

Dear LLVM developers -- this is my first contribution to the LLVM project, I hope I got it right.

Note that I am adding a new C-API function, and that should in principle be covered by tests. However, it was not sure to me where such a test would be added.

The only systematic tests of the C API I could find were really specific to certain components like ./unittests/Passes/PassBuilderBindingsTest.cpp or unittests/ExecutionEngine/MCJIT/MCJITCAPITest.cpp. I am open to any suggestions.

[nikic]

There are tests for the C API in llvm/tools/llvm-c-test, but maybe this is a bit inconvenient in this case. It would be possible to add a new unit test file like llvm/unittests/IR/Core.cpp or so as well.

[wjakob]

I added a testcase and ran arcanist again, which created a child differential D139460. I hope that's right.

[nikic]

In D139381#3975868, @wjakob wrote:

I added a testcase and ran arcanist again, which created a child differential D139460. I hope that's right.

The tests should be part of the same differential revision. I don't use arcanist, but you probably need to squash the two commits locally.

[wjakob]

Thanks, that sounds more reasonable. I closed the other differential and updated this one with a squashed commit.

[nikic]

llvm/include/llvm-c/Core.h

490

nit: Variable names should be upper case.

llvm/unittests/IR/CoreBindings.cpp

16 ↗

(On Diff #480788)

nit: Unnecessary newline.

[wjakob]

Removed superfluous newline.

[wjakob]

Changed variable case

[nikic]

LGTM. What Name <email> should be used for the commit?

[wjakob]

Thank you. Please use

Wenzel Jakob <[e-mail]>

llvm/include/llvm-c/Core.h

 
 void LLVMInitializeCore(LLVMPassRegistryRef R);
 
 /** Deallocate and destroy all ManagedStatic variables.
     @see llvm::llvm_shutdown
     @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);
 void LLVMDisposeMessage(char *Message);
 
 /**
  * @defgroup LLVMCCoreContext Contexts
  *

llvm/lib/IR/Core.cpp

 void LLVMInitializeCore(LLVMPassRegistryRef R) {
   initializeCore(*unwrap(R));
 }
 
 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) {
   return strdup(Message);
 }
 
 void LLVMDisposeMessage(char *Message) {
   free(Message);