68 lines
2.7 KiB
Diff
68 lines
2.7 KiB
Diff
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# reason: FTBFS with gcc9
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# src: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=925811
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From c35a3f519007af44c3b364b9af86f6a336f6411b Mon Sep 17 00:00:00 2001
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From: Thiago Macieira <thiago.macieira@intel.com>
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Date: Tue, 11 Feb 2014 16:17:46 -0800
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Subject: [PATCH] Redo the Q_FOREACH loop control without GCC statement
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expressions
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It's possible to do without them, which probably makes the number of
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supported compilers a lot bigger: they just need to support decltype()
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or __typeof__.
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That includes the Intel compiler. The old code was also apparently
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working, but no one had realized the old workaround for some old version
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was still in place.
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The loop overhead is more or less the same. I have not done benchmarks,
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but inspection of the generated assembly shows more or less the same
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number of instructions.
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Change-Id: I32d499c84a6ddd19d994b49f17a469acb5c3a3f1
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Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
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Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
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Backported to Qt 4
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--- a/src/corelib/global/qglobal.h
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+++ b/src/corelib/global/qglobal.h
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@@ -2482,22 +2482,32 @@ typedef uint Flags;
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#endif /* Q_NO_TYPESAFE_FLAGS */
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-#if defined(Q_CC_GNU) && !defined(Q_CC_INTEL) && !defined(Q_CC_RVCT)
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+#if (defined(Q_CC_GNU) && !defined(Q_CC_RVCT))
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/* make use of typeof-extension */
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template <typename T>
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class QForeachContainer {
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public:
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- inline QForeachContainer(const T& t) : c(t), brk(0), i(c.begin()), e(c.end()) { }
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+ inline QForeachContainer(const T& t) : c(t), i(c.begin()), e(c.end()), control(1) { }
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const T c;
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int brk;
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typename T::const_iterator i, e;
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+ int control;
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};
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+// Explanation of the control word:
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+// - it's initialized to 1
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+// - that means both the inner and outer loops start
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+// - if there were no breaks, at the end of the inner loop, it's set to 0, which
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+// causes it to exit (the inner loop is run exactly once)
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+// - at the end of the outer loop, it's inverted, so it becomes 1 again, allowing
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+// the outer loop to continue executing
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+// - if there was a break inside the inner loop, it will exit with control still
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+// set to 1; in that case, the outer loop will invert it to 0 and will exit too
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#define Q_FOREACH(variable, container) \
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for (QForeachContainer<__typeof__(container)> _container_(container); \
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- !_container_.brk && _container_.i != _container_.e; \
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- __extension__ ({ ++_container_.brk; ++_container_.i; })) \
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- for (variable = *_container_.i;; __extension__ ({--_container_.brk; break;}))
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+ _container_.control && _container_.i != _container_.e; \
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+ ++_container_.i, _container_.control ^= 1) \
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+ for (variable = *_container_.i; _container_.control; _container_.control = 0)
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#else
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