Fix #975 by overallocating memory to leave spare for PV to use

diff --git a/pv/data/segment.cpp b/pv/data/segment.cpp
index 9b18c6499a1b32cf03362dc67e835f410acb9159..7b8e611f271999d6b3a57948166322faccaa71bf 100644 (file)
--- a/pv/data/segment.cpp
+++ b/pv/data/segment.cpp
@@ -24,6 +24,7 @@
 #include <cstdlib>
 #include <cstring>
 
+using std::bad_alloc;
 using std::lock_guard;
 using std::min;
 using std::recursive_mutex;
@@ -116,15 +117,17 @@ void Segment::free_unused_memory()
                return;
        }
 
-       // No more data will come in, so re-create the last chunk accordingly
-       uint8_t* resized_chunk = new uint8_t[used_samples_ * unit_size_];
-       memcpy(resized_chunk, current_chunk_, used_samples_ * unit_size_);
+       if (current_chunk_) {
+               // No more data will come in, so re-create the last chunk accordingly
+               uint8_t* resized_chunk = new uint8_t[used_samples_ * unit_size_];
+               memcpy(resized_chunk, current_chunk_, used_samples_ * unit_size_);
 
-       delete[] current_chunk_;
-       current_chunk_ = resized_chunk;
+               delete[] current_chunk_;
+               current_chunk_ = resized_chunk;
 
-       data_chunks_.pop_back();
-       data_chunks_.push_back(resized_chunk);
+               data_chunks_.pop_back();
+               data_chunks_.push_back(resized_chunk);
+       }
 }
 
 void Segment::append_single_sample(void *data)
@@ -177,8 +180,26 @@ void Segment::append_samples(void* data, uint64_t samples)
                data_offset += (copy_count * unit_size_);
 
                if (unused_samples_ == 0) {
-                       // If we're out of memory, this will throw std::bad_alloc
-                       current_chunk_ = new uint8_t[chunk_size_];
+                       try {
+                               // If we're out of memory, allocating a chunk will throw
+                               // std::bad_alloc. To give the application some usable memory
+                               // to work with in case chunk allocation fails, we allocate
+                               // extra memory and throw it away if it all succeeded.
+                               // This way, memory allocation will fail early enough to let
+                               // PV remain alive. Otherwise, PV will crash in a random
+                               // memory-allocating part of the application.
+                               current_chunk_ = new uint8_t[chunk_size_];
+
+                               const int dummy_size = 2 * chunk_size_;
+                               auto dummy_chunk = new uint8_t[dummy_size];
+                               memset(dummy_chunk, 0xFF, dummy_size);
+                               delete[] dummy_chunk;
+                       } catch (bad_alloc) {
+                               delete[] current_chunk_;  // The new may have succeeded
+                               current_chunk_ = nullptr;
+                               throw;
+                       }
+
                        data_chunks_.push_back(current_chunk_);
                        used_samples_ = 0;
                        unused_samples_ = chunk_size_ / unit_size_;