Create a helper wrapper / abstraction for managing srcfiles lists

src/symbols/dwarf/dwarf.hpp

@@ -531,6 +531,56 @@ namespace libdwarf {
             }
         }
     };
+
+    class srcfiles {
+        Dwarf_Debug dbg = nullptr;
+        char** dw_srcfiles = nullptr;
+        Dwarf_Unsigned dw_filecount = 0;
+    public:
+        srcfiles(Dwarf_Debug dbg, char** dw_srcfiles, Dwarf_Signed filecount)
+            : dbg(dbg), dw_srcfiles(dw_srcfiles), dw_filecount(static_cast<Dwarf_Unsigned>(filecount))
+        {
+            if(filecount < 0) {
+                throw internal_error(microfmt::format("Unexpected dw_filecount {}", filecount));
+            }
+        }
+        ~srcfiles() {
+            if(dw_srcfiles) {
+                for(unsigned i = 0; i < dw_filecount; i++) {
+                    dwarf_dealloc(dbg, dw_srcfiles[i], DW_DLA_STRING);
+                    dw_srcfiles[i] = nullptr;
+                }
+                dwarf_dealloc(dbg, dw_srcfiles, DW_DLA_LIST);
+            }
+        }
+        srcfiles(const srcfiles&) = delete;
+        srcfiles(srcfiles&& other) {
+            std::swap(dbg, other.dbg);
+            std::swap(dw_srcfiles, other.dw_srcfiles);
+            std::swap(dw_filecount, other.dw_filecount);
+        }
+        srcfiles& operator=(const srcfiles&) = delete;
+        srcfiles& operator=(srcfiles&& other) {
+            std::swap(dbg, other.dbg);
+            std::swap(dw_srcfiles, other.dw_srcfiles);
+            std::swap(dw_filecount, other.dw_filecount);
+            return *this;
+        }
+        // note: dwarf uses 1-indexing
+        const char* get(Dwarf_Unsigned file_i) const {
+            if(file_i >= dw_filecount) {
+                throw internal_error(microfmt::format(
+                    "Error while accessing the srcfiles list, requested index {} is out of bounds (count = {})",
+                    file_i,
+                    dw_filecount
+                ));
+            }
+            return dw_srcfiles[file_i];
+        }
+        Dwarf_Unsigned count() const {
+            return dw_filecount;
+        }
+    };
 }
 }
 }

src/symbols/dwarf/dwarf_resolver.cpp

@@ -93,7 +93,7 @@ namespace libdwarf {
         std::vector<cu_entry> cu_cache;
         bool generated_cu_cache = false;
         // Map from CU -> {srcfiles, count}
-        std::unordered_map<Dwarf_Off, std::pair<char**, Dwarf_Signed>> srcfiles_cache;
+        std::unordered_map<Dwarf_Off, srcfiles> srcfiles_cache;
         // Map from CU -> split full cu resolver
         std::unordered_map<Dwarf_Off, std::unique_ptr<dwarf_resolver>> split_full_cu_resolvers;
         // info for resolving a dwo object
@@ -205,15 +205,6 @@ namespace libdwarf {
             for(auto& entry : line_tables) {
                 dwarf_srclines_dealloc_b(entry.second.line_context);
             }
-            for(auto& entry : srcfiles_cache) {
-                auto srcfiles = entry.second.first;
-                auto count = entry.second.second;
-                for(int i = 0; i < count; i++) {
-                    dwarf_dealloc(dbg, srcfiles[i], DW_DLA_STRING);
-                    srcfiles[i] = nullptr;
-                }
-                dwarf_dealloc(dbg, srcfiles, DW_DLA_LIST);
-            }
             // subprograms_cache needs to be destroyed before dbg otherwise there will be another use after free
             subprograms_cache.clear();
             split_full_cu_resolvers.clear();
@@ -354,15 +345,11 @@ namespace libdwarf {
                 char** dw_srcfiles;
                 Dwarf_Signed dw_filecount;
                 VERIFY(wrap(dwarf_srcfiles, cu_die.get(), &dw_srcfiles, &dw_filecount) == DW_DLV_OK);
+                srcfiles srcfiles(cu_die.dbg, dw_srcfiles, dw_filecount);
                 if(Dwarf_Signed(file_i) < dw_filecount) {
                     // dwarf is using 1-indexing
-                    filename = dw_srcfiles[file_i];
+                    filename = srcfiles.get(file_i);
                 }
-                for(int i = 0; i < dw_filecount; i++) {
-                    dwarf_dealloc(cu_die.dbg, dw_srcfiles[i], DW_DLA_STRING);
-                    dw_srcfiles[i] = nullptr;
-                }
-                dwarf_dealloc(cu_die.dbg, dw_srcfiles, DW_DLA_LIST);
             } else {
                 auto off = cu_die.get_global_offset();
                 auto it = srcfiles_cache.find(off);
@@ -370,13 +357,11 @@ namespace libdwarf {
                     char** dw_srcfiles;
                     Dwarf_Signed dw_filecount;
                     VERIFY(wrap(dwarf_srcfiles, cu_die.get(), &dw_srcfiles, &dw_filecount) == DW_DLV_OK);
-                    it = srcfiles_cache.insert(it, {off, {dw_srcfiles, dw_filecount}});
+                    it = srcfiles_cache.insert(it, {off, srcfiles{cu_die.dbg, dw_srcfiles, dw_filecount}});
                 }
-                char** dw_srcfiles = it->second.first;
+                if(file_i < it->second.count()) {
-                Dwarf_Signed dw_filecount = it->second.second;
-                if(Dwarf_Signed(file_i) < dw_filecount) {
                     // dwarf is using 1-indexing
-                    filename = dw_srcfiles[file_i];
+                    filename = it->second.get(file_i);
                 }
             }
             return filename;