Explicitly use libstdc++ for non-C++11 static builds

Otherwise the compiler may choose libc++ based on the deployment target,
and we'll end up with broken builds due to the mismatch between the two
libraries, eg:

Undefined symbols for architecture x86_64:
  "std::ios_base::Init::Init()", referenced from:
      __GLOBAL__I_a in libQt5Qml.a(qv4object.o)
      ...
  "std::ios_base::Init::~Init()", referenced from:
      __GLOBAL__I_a in libQt5Qml.a(qv4object.o)
      ...
  "std::__throw_length_error(char const*)", referenced from:
      ...

This problem is not iOS specific, which is why the logic is moved
to the more generic mac/default_post.prf.

Change-Id: I28b94e614f9167fc0db84bbf1c88dd97d5629938
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/mkspecs/features/mac/default_post.prf b/mkspecs/features/mac/default_post.prf
index 614b336f27..da3e22b5f3 100644
--- a/mkspecs/features/mac/default_post.prf
+++ b/mkspecs/features/mac/default_post.prf
@@ -25,6 +25,15 @@ qt:!isEmpty(QT_CONFIG) {
             warning("Qt was not built with C++11 enabled, disabling feature")
             CONFIG -= c++11
         }
+
+        !c++11 {
+            # Explicitly use libstdc++ if C++11 support is not enabled,
+            # as otherwise the compiler will choose the standard library
+            # based on the deployment target, which for iOS 7 and OS X 10.9
+            # is libc++, and we can't mix and match the two.
+            QMAKE_CXXFLAGS += -stdlib=libstdc++
+            QMAKE_LFLAGS   += -stdlib=libstdc++
+        }
     }
 }