storage/curl: move start call out of the constructor

This can cause request completion in the I/O thread before this constructor returns, leaving the object in an abstract state, causing a crash due to pure virtual method call. We should not start the request until this object is fully constructed. Closes https://github.com/MusicPlayerDaemon/MPD/issues/665

storage/curl: move start call out of the constructor
d01fb673 · Max Kellermann · 7bfe6a33 · d01fb673 · d01fb673
Commit d01fb673 authored Dec 23, 2019 by Max Kellermann
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NEWS NEWS +2 -0

CurlStorage.cxx src/storage/plugins/CurlStorage.cxx +5 -0

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--- a/NEWS
+++ b/NEWS
 ver 0.21.18 (not yet released)
 * output
  - alsa: fix hang bug with ALSA "null" outputs
+* storage
+  - curl: fix crash bug
 * reduce unnecessary CPU wakeups

 ver 0.21.17 (2019/12/16)

--- a/src/storage/plugins/CurlStorage.cxx
+++ b/src/storage/plugins/CurlStorage.cxx
@@ -109,7 +109,9 @@ public:
 			     BIND_THIS_METHOD(OnDeferredStart)),
 		 request(curl, uri, *this) {
 		// TODO: use CurlInputStream's configuration
+	}

+	void DeferStart() noexcept {
 		/* start the transfer inside the IOThread */
 		defer_start.Schedule();
 	}
@@ -283,6 +285,7 @@ public:
 	}

 	using BlockingHttpRequest::GetEasy;
+	using BlockingHttpRequest::DeferStart;
 	using BlockingHttpRequest::Wait;

 protected:
@@ -430,6 +433,7 @@ public:
 	}

 	const StorageFileInfo &Perform() {
+		DeferStart();
 		Wait();
 		return info;
 	}
@@ -481,6 +485,7 @@ public:
 		 base_path(UriPathOrSlash(uri)) {}

 	std::unique_ptr<StorageDirectoryReader> Perform() {
+		DeferStart();
 		Wait();
 		return ToReader();
 	}