fixup! Ensure cluster cache is properly clean in case of exception in constructor.

Calling non static member from constructor try block handler is UB.
Accessing this (witohut dereferencing it) is kind of gray area as
(See https://stackoverflow.com/questions/79463018/can-i-access-this-from-contructor-try-block-handler)

So the try/catch has been moved to a more classic try/catch block as
only a specific part of the contructor can create (and cache) clusters.

Author: mgautierfr

src/fileimpl.cpp

@@ -188,7 +188,7 @@ class Grouping
   {}
 #endif
 
-  FileImpl::FileImpl(std::shared_ptr<FileCompound> _zimFile) try
+  FileImpl::FileImpl(std::shared_ptr<FileCompound> _zimFile)
     : zimFile(_zimFile),
       zimReader(makeFileReader(zimFile)),
       direntReader(new DirentReader(zimReader)),
@@ -248,33 +248,42 @@ class Grouping
       const_cast<entry_index_t&>(m_endUserEntry) = getCountArticles();
     }
 
-    auto result = tmp_direntLookup.find('X', "listing/titleOrdered/v1");
-    if (result.first) {
-      mp_titleDirentAccessor = getTitleAccessorV1(result.second);
-    }
 
-    if (!mp_titleDirentAccessor) {
-      if (!header.hasTitleListingV0()) {
-        throw ZimFileFormatError("Zim file doesn't contain a title ordered index");
+    // Following code will may create cluster and
+    try {
+      auto result = tmp_direntLookup.find('X', "listing/titleOrdered/v1");
+      if (result.first) {
+        mp_titleDirentAccessor = getTitleAccessorV1(result.second);
       }
-      offset_t titleOffset(header.getTitleIdxPos());
-      zsize_t  titleSize(sizeof(entry_index_type)*header.getArticleCount());
-      mp_titleDirentAccessor = getTitleAccessor(titleOffset, titleSize, "Title index table");
-      const_cast<bool&>(m_hasFrontArticlesIndex) = false;
-    }
-    m_byTitleDirentLookup.reset(new ByTitleDirentLookup(mp_titleDirentAccessor.get()));
 
-    readMimeTypes();
-  } catch (...) {
-    getClusterCache().drop_all([=](const std::tuple<FileImpl*, cluster_index_type>& key) {return std::get<0>(key) == this;});
-    throw;
+      if (!mp_titleDirentAccessor) {
+        if (!header.hasTitleListingV0()) {
+          throw ZimFileFormatError("Zim file doesn't contain a title ordered index");
+        }
+        offset_t titleOffset(header.getTitleIdxPos());
+        zsize_t  titleSize(sizeof(entry_index_type)*header.getArticleCount());
+        mp_titleDirentAccessor = getTitleAccessor(titleOffset, titleSize, "Title index table");
+        const_cast<bool&>(m_hasFrontArticlesIndex) = false;
+      }
+      m_byTitleDirentLookup.reset(new ByTitleDirentLookup(mp_titleDirentAccessor.get()));
+
+      readMimeTypes();
+    } catch (...) {
+      dropCachedCluster();
+      throw;
+    }
   }
 
   FileImpl::~FileImpl() {
     // We have to clean the global cache for our clusters.
+    dropCachedCluster();
+  }
+
+  void FileImpl::dropCachedCluster() const {
     getClusterCache().drop_all([=](const std::tuple<FileImpl*, cluster_index_type>& key) {return std::get<0>(key) == this;});
   }
 
+
   std::unique_ptr<IndirectDirentAccessor> FileImpl::getTitleAccessorV1(const entry_index_t idx)
   {
     auto dirent = mp_pathDirentAccessor->getDirent(idx);

src/fileimpl.h

@@ -166,6 +166,8 @@ namespace zim
       explicit FileImpl(std::shared_ptr<FileCompound> zimFile);
       FileImpl(std::shared_ptr<FileCompound> zimFile, offset_t offset, zsize_t size);
 
+      void dropCachedCluster() const;
+
       std::unique_ptr<IndirectDirentAccessor> getTitleAccessorV1(const entry_index_t idx);
       std::unique_ptr<IndirectDirentAccessor> getTitleAccessor(const offset_t offset, const zsize_t size, const std::string& name);