From: Soeren Apel <redacted>
Date: Wed, 30 May 2018 21:56:29 +0000 (+0200)
Subject: Fix #975 by overallocating memory to leave spare for PV to use
X-Git-Url: https://sigrok.org/gitweb/?p=pulseview.git;a=commitdiff_plain;h=2c39cfe261f46ba4dd97a403a51e6c11893b6b0a;ds=sidebyside

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 9b18c649..7b8e611f 100644
--- 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_;