Pass callback parameters by value to avoid dangling references

Resolves #3483
Resolves #3487

Author: rocallahan

src/AddressSpace.cc

@@ -886,11 +886,10 @@ void AddressSpace::protect(Task* t, remote_ptr<void> addr, size_t num_bytes,
              << ")";
 
   MemoryRange last_overlap;
-  auto protector = [this, prot, &last_overlap](const Mapping& mm,
-                                               const MemoryRange& rem) {
+  auto protector = [this, prot, &last_overlap](Mapping m,
+                                               MemoryRange rem) {
     LOG(debug) << "  protecting (" << rem << ") ...";
 
-    Mapping m = std::move(mm);
     remove_from_map(m.map);
 
     // PROT_GROWSDOWN means that if this is a grows-down segment
@@ -1305,10 +1304,9 @@ void AddressSpace::unmap_internal(Task*, remote_ptr<void> addr,
                                   ssize_t num_bytes) {
   LOG(debug) << "munmap(" << addr << ", " << num_bytes << ")";
 
-  auto unmapper = [this](const Mapping& mm, const MemoryRange& rem) {
+  auto unmapper = [this](Mapping m, MemoryRange rem) {
     LOG(debug) << "  unmapping (" << rem << ") ...";
 
-    Mapping m = std::move(mm);
     remove_from_map(m.map);
 
     LOG(debug) << "  erased (" << m.map << ") ...";
@@ -1548,12 +1546,11 @@ void AddressSpace::ensure_replay_matches_single_recorded_mapping(Task* t, Memory
   ASSERT(t, range.start() == floor_page_size(range.start()));
   ASSERT(t, range.end() == ceil_page_size(range.end()));
 
-  auto fixer = [this, t, range](const Mapping& mm, const MemoryRange&) {
-    if (mm.map == range) {
+  auto fixer = [this, t, range](Mapping mapping, MemoryRange) {
+    if (mapping.map == range) {
       // Existing single mapping covers entire range; nothing to do.
       return;
     }
-    Mapping mapping = std::move(mm);
 
     // These should be null during replay
     ASSERT(t, !mapping.mapped_file_stat);
@@ -2006,7 +2003,7 @@ void AddressSpace::maybe_update_breakpoints(Task* t, remote_ptr<uint8_t> addr,
 
 void AddressSpace::for_each_in_range(
     remote_ptr<void> addr, ssize_t num_bytes,
-    function<void(const Mapping& m, const MemoryRange& rem)> f, int how) {
+    function<void(Mapping m, MemoryRange rem)> f, int how) {
   remote_ptr<void> region_start = floor_page_size(addr);
   remote_ptr<void> last_unmapped_end = region_start;
   remote_ptr<void> region_end = ceil_page_size(addr + num_bytes);

src/AddressSpace.h

@@ -957,11 +957,14 @@ class AddressSpace : public HasTaskSet {
    * Pass |ITERATE_CONTIGUOUS| to stop iterating when the last
    * contiguous mapping after |addr| within the region is seen.
    * Default is to iterate all mappings in the region.
+   *
+   * The callback takes parameters by value to avoid dangling
+   * references if the memory map is modified inside the callback.
    */
   enum { ITERATE_DEFAULT, ITERATE_CONTIGUOUS };
   void for_each_in_range(
       remote_ptr<void> addr, ssize_t num_bytes,
-      std::function<void(const Mapping& m, const MemoryRange& rem)> f,
+      std::function<void(Mapping m, MemoryRange rem)> f,
       int how = ITERATE_DEFAULT);
 
   /**