GDALAlgorithm: fix invalid C++ use that caused crashed with gcc 14.2 / Alpine

Author: rouault

gcore/gdalalgorithm.cpp

@@ -215,6 +215,12 @@ GDALAlgorithmArgDecl &GDALAlgorithmArgDecl::SetMaxCount(int count)
     return *this;
 }
 
+/************************************************************************/
+/*                 GDALAlgorithmArg::~GDALAlgorithmArg()                */
+/************************************************************************/
+
+GDALAlgorithmArg::~GDALAlgorithmArg() = default;
+
 /************************************************************************/
 /*                         GDALAlgorithmArg::Set()                      */
 /************************************************************************/
@@ -2146,7 +2152,7 @@ GDALAlgorithm::AddArg(std::unique_ptr<GDALInConstructionAlgorithmArg> arg)
     }
     m_args.emplace_back(std::move(arg));
     return *(
-        static_cast<GDALInConstructionAlgorithmArg *>(m_args.back().get()));
+        cpl::down_cast<GDALInConstructionAlgorithmArg *>(m_args.back().get()));
 }
 
 GDALInConstructionAlgorithmArg &

gcore/gdalalgorithm.h

@@ -1161,6 +1161,9 @@ class CPL_DLL GDALAlgorithmArg /* non-final */
         }
     }
 
+    /** Destructor */
+    virtual ~GDALAlgorithmArg();
+
     /** Return the argument declaration. */
     const GDALAlgorithmArgDecl &GetDeclaration() const
     {