llvm-mc: Error on MCSubtargetInfo construction failure

[arsenm]

We have inconsistent handling of null returns on target MC constructors. Most tools report an error, but some assert. It's currently not possible to test this with any in-tree targets. Make this a clean error so in the future targets can fail the construction.

[arsenm]

• llvm-mc: Error on MCSubtargetInfo construction failure #159226 👈 (View in Graphite)
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[llvmbot]

@llvm/pr-subscribers-llvm-mc

Author: Matt Arsenault (arsenm)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/159226.diff

1 Files Affected:

• (modified) llvm/tools/llvm-mc/llvm-mc.cpp (+4-1)

diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index 136cd69526a3c..224fd80f6a6d3 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -469,7 +469,10 @@ int main(int argc, char **argv) {
 
   std::unique_ptr<MCSubtargetInfo> STI(
       TheTarget->createMCSubtargetInfo(TheTriple, MCPU, FeaturesStr));
-  assert(STI && "Unable to create subtarget info!");
+  if (!STI) {
+    WithColor::error(errs(), ProgName) << "unable to create subtarget info\n";
+    return 1;
+  }
 
   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and
   // MCObjectFileInfo needs a MCContext reference in order to initialize itself.

[MaskRay]

Can you add a test to llvm/test/tools/llvm-mc?

% llvm-mc -triple=xxx
llvm-mc: error: unable to get target for 'xxx', see --version and --triple.

[arsenm]

Can you add a test to llvm/test/tools/llvm-mc?

Short answer is no

% llvm-mc -triple=xxx
llvm-mc: error: unable to get target for 'xxx', see --version and --triple.

This is a different error for the top level target machine. There is no current in tree example where the subtarget constructor will return nullptr (but it probably should be a failable method that returns with error messages). Currently this would only trigger on partially implemented targets

[MaskRay]

Should edit the description that testing is not feasible.