[NFC] Check for defined(__GNUC__) before use

[DavidTruby]

This silences some spurious warnings on Windows builds with clang-cl that __GNUC__ is
not defined if -Wundef is passed, which is the default in MLIR.
These warnings make Windows builds of LLVM very noisy when MLIR is included.

[llvmbot]

@llvm/pr-subscribers-llvm-adt

Author: David Truby (DavidTruby)

Changes

This silences some spurious warnings on Windows builds that GNUC is
not defined. These warnings make Windows builds very noisy.

---

Full diff: https://github.com/llvm/llvm-project/pull/116076.diff

1 Files Affected:

• (modified) llvm/include/llvm/ADT/iterator_range.h (+2-1)

diff --git a/llvm/include/llvm/ADT/iterator_range.h b/llvm/include/llvm/ADT/iterator_range.h
index 6c66def0fcd77b..8e9b22f2d4dfa7 100644
--- a/llvm/include/llvm/ADT/iterator_range.h
+++ b/llvm/include/llvm/ADT/iterator_range.h
@@ -43,7 +43,8 @@ class iterator_range {
   IteratorT begin_iterator, end_iterator;
 
 public:
-#if __GNUC__ == 7 || (__GNUC__ == 8 && __GNUC_MINOR__ < 4)
+#if defined(__GNUC__) &&                                                       \
+    (__GNUC__ == 7 || (__GNUC__ == 8 && __GNUC_MINOR__ < 4))
   // Be careful no to break gcc-7 and gcc-8 < 8.4 on the mlir target.
   // See https://github.com/llvm/llvm-project/issues/63843
   template <typename Container>

[zero9178]

LGTM thank you! Ran into this recently as well and can confirm this fixes it

Might be worth being more precise in the commit message that this only happens when using clang-cl and -Wundef, which MLIR does eg. So this is even an in-tree issue

[RoboTux]

LGTM as well, thanks for the fix.