qt: Fix build with GCC9 for version 4 (#12832)

* qt: Fix build w/ GCC9 for @4:

* qt: Fix patch filename and qt version

* Fix typo in patch name

2 files changed, 68 insertions, 0 deletions

diff --git a/var/spack/repos/builtin/packages/qt/package.py b/var/spack/repos/builtin/packages/qt/package.py
index 158b9b6e3e..8b192de89f 100644
--- a/var/spack/repos/builtin/packages/qt/package.py
+++ b/var/spack/repos/builtin/packages/qt/package.py
@@ -105,6 +105,10 @@ class Qt(Package):
           working_dir='qtbase',
           when='@5.10:5.12.0 %gcc@9:')
 
+    # Fix build of QT4 with GCC 9
+    # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=925811
+    patch("qt4-gcc9-qforeach.patch", when="@4:4.999 %gcc@9")
+
     # https://bugreports.qt.io/browse/QTBUG-74196
     # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89585
     patch('qt4-gcc8.3-asm-volatile-fix.patch', when='@4')
diff --git a/var/spack/repos/builtin/packages/qt/qt4-gcc9-qforeach.patch b/var/spack/repos/builtin/packages/qt/qt4-gcc9-qforeach.patch
new file mode 100644
index 0000000000..ae54cdbc1e
--- /dev/null
+++ b/var/spack/repos/builtin/packages/qt/qt4-gcc9-qforeach.patch
@@ -0,0 +1,64 @@
+From c35a3f519007af44c3b364b9af86f6a336f6411b Mon Sep 17 00:00:00 2001
+From: Thiago Macieira <thiago.macieira@intel.com>
+Date: Tue, 11 Feb 2014 16:17:46 -0800
+Subject: [PATCH] Redo the Q_FOREACH loop control without GCC statement
+ expressions
+
+It's possible to do without them, which probably makes the number of
+supported compilers a lot bigger: they just need to support decltype()
+or __typeof__.
+
+That includes the Intel compiler. The old code was also apparently
+working, but no one had realized the old workaround for some old version
+was still in place.
+
+The loop overhead is more or less the same. I have not done benchmarks,
+but inspection of the generated assembly shows more or less the same
+number of instructions.
+
+Change-Id: I32d499c84a6ddd19d994b49f17a469acb5c3a3f1
+Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
+Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
+
+Backported to Qt 4
+
+--- a/src/corelib/global/qglobal.h
++++ b/src/corelib/global/qglobal.h
+@@ -2482,22 +2482,32 @@ typedef uint Flags;
+ 
+ #endif /* Q_NO_TYPESAFE_FLAGS */
+ 
+-#if defined(Q_CC_GNU) && !defined(Q_CC_INTEL) && !defined(Q_CC_RVCT)
++#if (defined(Q_CC_GNU) && !defined(Q_CC_RVCT))
+ /* make use of typeof-extension */
+ template <typename T>
+ class QForeachContainer {
+ public:
+-    inline QForeachContainer(const T& t) : c(t), brk(0), i(c.begin()), e(c.end()) { }
++    inline QForeachContainer(const T& t) : c(t), i(c.begin()), e(c.end()), control(1) { }
+     const T c;
+     int brk;
+     typename T::const_iterator i, e;
++    int control;
+ };
+ 
++// Explanation of the control word:
++//  - it's initialized to 1
++//  - that means both the inner and outer loops start
++//  - if there were no breaks, at the end of the inner loop, it's set to 0, which
++//    causes it to exit (the inner loop is run exactly once)
++//  - at the end of the outer loop, it's inverted, so it becomes 1 again, allowing
++//    the outer loop to continue executing
++//  - if there was a break inside the inner loop, it will exit with control still
++//    set to 1; in that case, the outer loop will invert it to 0 and will exit too
+ #define Q_FOREACH(variable, container)                                \
+ for (QForeachContainer<__typeof__(container)> _container_(container); \
+-     !_container_.brk && _container_.i != _container_.e;              \
+-     __extension__  ({ ++_container_.brk; ++_container_.i; }))                       \
+-    for (variable = *_container_.i;; __extension__ ({--_container_.brk; break;}))
++     _container_.control && _container_.i != _container_.e;         \
++     ++_container_.i, _container_.control ^= 1)                     \
++    for (variable = *_container_.i; _container_.control; _container_.control = 0)
+ 
+ #else
+