meson: fix LLVM version detection when <= 3.4

3 digits versions in LLVM only started from 3.4.1 on.

Hence, even if you can perfectly build with an old LLVM (< 3.4.1) in
the system while not needing LLVM at all (auto), when passing through
the LLVM version detection code, meson will fail when accessing
"_llvm_version[2]" due to:

"Index 2 out of bounds of array of size 2."

v2: Properly compare LLVM version and set patch version to 0
    if < 3.4.1 (Eric).

v3: Improve the commit log explanation (Eric).

Cc: Dylan Baker <[email protected]>
Cc: Eric Engestrom <[email protected]>
Signed-off-by: Andres Gomez <[email protected]>
Reviewed-by: Dylan Baker <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>
Reviewed-by: Eric Engestrom <[email protected]>

1 files changed, 8 insertions, 1 deletions

diff --git a/meson.build b/meson.build
index 308f64cf811..e9928a37931 100644
--- a/meson.build
+++ b/meson.build
@@ -1037,7 +1037,14 @@ if with_llvm
   # that for our version checks.
   # svn suffixes are stripped by meson as of 0.43, and git suffixes are
   # strippped as of 0.44, but we support older meson versions.
-  _llvm_patch = _llvm_version[2]
+
+  # 3 digits versions in LLVM only started from 3.4.1 on
+  if dep_llvm.version().version_compare('>= 3.4.1')
+    _llvm_patch = _llvm_version[2]
+  else
+    _llvm_patch = '0'
+  endif
+
   if _llvm_patch.endswith('svn')
     _llvm_patch = _llvm_patch.split('s')[0]
   elif _llvm_patch.contains('git')