[LyX/master] Fix #9490: SIGSEGV involving LyX macros --- A reproducible MWE (part II)

[Enrico Forestieri]

commit 82fe5183ca494fccc745953a9771ab7423a84693
Author: Enrico Forestieri <for...@lyx.org>
Date:   Sat Oct 3 17:41:25 2015 +0200

    Fix #9490: SIGSEGV involving LyX macros --- A reproducible MWE (part II)

diff --git a/src/mathed/MathMacro.cpp b/src/mathed/MathMacro.cpp
index 7901128..e01f7c2 100644
--- a/src/mathed/MathMacro.cpp
+++ b/src/mathed/MathMacro.cpp
@@ -63,6 +63,8 @@ public:
        ///
        void setOwner(MathMacro * mathMacro) { mathMacro_ = mathMacro; }
        ///
+       MathMacro const * owner() { return mathMacro_; }
+       ///
        InsetCode lyxCode() const { return ARGUMENT_PROXY_CODE; }
        ///
        void metrics(MetricsInfo & mi, Dimension & dim) const {
@@ -151,6 +153,9 @@ public:
        /// This needs to be called every time a copy of the owner is created
        /// (bug 9418).
        void updateChildren(MathMacro * owner);
+       /// Recursively update the pointers of all expanded macros
+       /// appearing in the arguments of the current macro
+       void updateNestedChildren(MathMacro * owner, InsetMathNest * ni);
        /// name of macro
        docstring name_;
        /// current display mode
@@ -190,17 +195,46 @@ void MathMacro::Private::updateChildren(MathMacro * owner)
                ArgumentProxy * p = dynamic_cast<ArgumentProxy 
*>(expanded_[i].nucleus());
                if (p)
                        p->setOwner(owner);
+
+               InsetMathNest * ni = expanded_[i].nucleus()->asNestInset();
+               if (ni)
+                       updateNestedChildren(owner, ni);
        }
 
-       if (macro_ && lyxrc.preview == LyXRC::PREVIEW_ON) {
-               // As MathData::metrics() is not called when instant preview is
-               // on, we have to update macro_ by ourselves. In this case, we
-               // simply let it point to the last known good copy of MacroData.
+       if (macro_) {
+               // The macro_ pointer is updated when MathData::metrics() is
+               // called. However, when instant preview is on or the macro is
+               // not on screen, MathData::metrics() is not called and we may
+               // have a dangling pointer. As a safety measure, when a macro
+               // is copied, always let macro_ point to the backup copy of the
+               // MacroData structure. This backup is updated every time the
+               // macro is changed, so it will not become stale.
                macro_ = &macroBackup_;
        }
 }
 
 
+void MathMacro::Private::updateNestedChildren(MathMacro * owner, InsetMathNest 
* ni)
+{
+       for (size_t i = 0; i < ni->nargs(); ++i) {
+               MathData & ar = ni->cell(i);
+               for (size_t j = 0; j < ar.size(); ++j) {
+                       ArgumentProxy * ap = dynamic_cast
+                               <ArgumentProxy *>(ar[j].nucleus());
+                       if (ap) {
+                               MathMacro::Private * md = ap->owner()->d;
+                               if (md->macro_)
+                                       md->macro_ = &md->macroBackup_;
+                               ap->setOwner(owner);
+                       }
+                       InsetMathNest * imn = ar[j].nucleus()->asNestInset();
+                       if (imn)
+                               updateNestedChildren(owner, imn);
+               }
+       }
+}
+
+
 MathMacro::MathMacro(Buffer * buf, docstring const & name)
        : InsetMathNest(buf, 0), d(new Private(buf, name))
 {}
@@ -209,6 +243,7 @@ MathMacro::MathMacro(Buffer * buf, docstring const & name)
 MathMacro::MathMacro(MathMacro const & that)
        : InsetMathNest(that), d(new Private(*that.d))
 {
+       setBuffer(*that.buffer_);
        d->updateChildren(this);
 }