From 99046d23d78d341674bbad3414567f362ffc60cd Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Sat, 13 Mar 2021 12:04:07 +0200
Subject: Tighten Clang detection not to misdetect GCC built with Clang

GitHub issue #136.
---
 libbuild2/cc/guess.cxx | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'libbuild2')

diff --git a/libbuild2/cc/guess.cxx b/libbuild2/cc/guess.cxx
index 1e0c77a..d80fd17 100644
--- a/libbuild2/cc/guess.cxx
+++ b/libbuild2/cc/guess.cxx
@@ -1016,6 +1016,8 @@ namespace build2
                     : guess_result ());
           }
 
+          size_t p;
+
           // The gcc -v output will have a last line in the form:
           //
           // "gcc version X.Y.Z ..."
@@ -1111,7 +1113,12 @@ namespace build2
           // The clang-cl output is exactly the same, which means the only way
           // to distinguish it is based on the executable name.
           //
-          if (l.find ("clang ") != string::npos)
+          // We must also watch out for potential misdetections, for example:
+          //
+          // Configured with: ../gcc/configure CC=clang CXX=clang++ ...
+          //
+          if ((p = l.find ("clang ")) != string::npos &&
+              (p == 0 || l[p - 1] == ' '))
           {
             if (cache.empty ())
             {
-- 
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