SYMBOL_LIBRARY_MANAGER: Clarify ownership semantics

DeleteBuffer took a std::shared_ptr by value. This means
it claims to take (and keep) part-ownership of the pointed-to
item. However, this function does not take any ownership or
change the item, it just refers to it. It also does not null-check
the pointer. So it should be a const reference to the item.
Ownership semantics are then: the caller retains ownership
while the function executes.

(It also saves a shared_ptr ref count, but that won't be
important here).

eeschema/symbol_library_manager.cpp

@@ -590,7 +590,7 @@ bool SYMBOL_LIBRARY_MANAGER::RemoveSymbol( const wxString& aAlias, const wxStrin
 
     bool retv = true;
 
-    retv &= libBuf.DeleteBuffer( symbolBuf );
+    retv &= libBuf.DeleteBuffer( *symbolBuf );
     OnDataChanged();
 
     return retv;
@@ -964,16 +964,21 @@ bool LIB_BUFFER::UpdateBuffer( std::shared_ptr<SYMBOL_BUFFER> aSymbolBuf, LIB_SY
 }
 
 
-bool LIB_BUFFER::DeleteBuffer( std::shared_ptr<SYMBOL_BUFFER> aSymbolBuf )
+bool LIB_BUFFER::DeleteBuffer( const SYMBOL_BUFFER& aSymbolBuf )
 {
-    auto symbolBufIt = std::find( m_symbols.begin(), m_symbols.end(), aSymbolBuf );
+    const auto sameBufferPredicate = [&]( const std::shared_ptr<SYMBOL_BUFFER>& aBuf )
+    {
+        return aBuf.get() == &aSymbolBuf;
+    };
+
+    auto symbolBufIt = std::find_if( m_symbols.begin(), m_symbols.end(), sameBufferPredicate );
     wxCHECK( symbolBufIt != m_symbols.end(), false );
 
     bool retv = true;
 
     // Remove all derived symbols to prevent broken inheritance.
-    if( HasDerivedSymbols( aSymbolBuf->GetSymbol()->GetName() )
-            && ( removeChildSymbols( aSymbolBuf ) == 0 ) )
+    if( HasDerivedSymbols( aSymbolBuf.GetSymbol()->GetName() )
+        && ( removeChildSymbols( aSymbolBuf ) == 0 ) )
     {
         retv = false;
     }
@@ -1219,15 +1224,13 @@ size_t LIB_BUFFER::GetDerivedSymbolNames( const wxString& aSymbolName, wxArraySt
 }
 
 
-int LIB_BUFFER::removeChildSymbols( std::shared_ptr<SYMBOL_BUFFER>& aSymbolBuf )
+int LIB_BUFFER::removeChildSymbols( const SYMBOL_BUFFER& aSymbolBuf )
 {
-    wxCHECK( aSymbolBuf, 0 );
-
     int                                                  cnt = 0;
     wxArrayString                                        derivedSymbolNames;
     std::deque<std::shared_ptr<SYMBOL_BUFFER>>::iterator it;
 
-    if( GetDerivedSymbolNames( aSymbolBuf->GetSymbol()->GetName(), derivedSymbolNames ) )
+    if( GetDerivedSymbolNames( aSymbolBuf.GetSymbol()->GetName(), derivedSymbolNames ) )
     {
         for( const wxString& symbolName : derivedSymbolNames )
         {

eeschema/symbol_library_manager.h

@@ -110,7 +110,10 @@ public:
     ///< Update the buffered symbol with the contents of \a aCopy.
     bool UpdateBuffer( std::shared_ptr<SYMBOL_BUFFER> aSymbolBuf, LIB_SYMBOL* aCopy );
 
-    bool DeleteBuffer( std::shared_ptr<SYMBOL_BUFFER> aSymbolBuf );
+    /**
+     * Delete the given symbol buffer from the library buffer.
+     */
+    bool DeleteBuffer( const SYMBOL_BUFFER& aSymbolBuf );
 
     void ClearDeletedBuffer() { m_deleted.clear(); }
 
@@ -160,7 +163,7 @@ private:
      * @param aParent is the #SYMBOL_BUFFER to check against.
      * @return the count of #SYMBOL_BUFFER objects removed from the library.
      */
-    int removeChildSymbols( std::shared_ptr<SYMBOL_BUFFER>& aSymbolBuf );
+    int removeChildSymbols( const SYMBOL_BUFFER& aSymbolBuf );
 
 private:
     std::deque<std::shared_ptr<SYMBOL_BUFFER>> m_symbols;

qa/tests/eeschema/test_symbol_library_manager.cpp

@@ -133,7 +133,8 @@ BOOST_AUTO_TEST_CASE( LibBuffer )
     BOOST_CHECK_EQUAL( libBuffer.GetHash(), 4 );
     BOOST_CHECK( *libBuffer.GetSymbol( parentSymbol1->GetName() ) == *tmp );
 
-    libBuffer.DeleteBuffer( buf );
+    const bool deletedOk = libBuffer.DeleteBuffer( *buf );
+    BOOST_CHECK( deletedOk );
     BOOST_CHECK( libBuffer.GetBuffers().empty() );
 }