1461540 - warning: ‘errorMessage’ may be used uninitialized, for MediaBufferDecoder.cpp:563:15

Status: RESOLVED FIXED

(Core :: Web Audio, defect, P3)

Description

[Chris Pearce [:cpearce (Not reading bugmail)]]

I see this warning building on Ubuntu with gcc (Ubuntu 7.2.0-8ubuntu3.2) 7.2.0:

 0:27.66 In file included from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/nsString.h:23:0,
 0:27.66                  from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/nsAtom.h:11,
 0:27.66                  from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/nsGkAtoms.h:10,
 0:27.66                  from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/mozilla/DOMEventTargetHelper.h:11,
 0:27.66                  from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/mozilla/dom/AudioNode.h:10,
 0:27.66                  from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/mozilla/dom/ChannelMergerNode.h:10,
 0:27.66                  from /home/cpearce/src/firefox/dom/media/webaudio/ChannelMergerNode.cpp:7,
 0:27.66                  from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dom/media/webaudio/Unified_cpp_dom_media_webaudio1.cpp:2:
 0:27.66 /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/nsTString.h: In member function ‘void mozilla::WebAudioDecodeJob::OnFailure(mozilla::WebAudioDecodeJob::ErrorCode)’:
 0:27.66 /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dist/include/nsTString.h:605:5: warning: ‘errorMessage’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 0:27.66      this->Assign(aData, aLength);
 0:27.66      ^~~~
 0:27.66 In file included from /home/cpearce/src/firefox/obj-x86_64-pc-linux-gnu/dom/media/webaudio/Unified_cpp_dom_media_webaudio1.cpp:92:0:
 0:27.66 /home/cpearce/src/firefox/dom/media/webaudio/MediaBufferDecoder.cpp:563:15: note: ‘errorMessage’ was declared here
 0:27.66    const char* errorMessage;
 0:27.66                ^~~~~~~~~~~~

Comment 1

[Chris Pearce [:cpearce (Not reading bugmail)]]

Attachment: Bug 1461540 - Ensure errorMessage is initialized on all code paths in WebAudioDecodeJob::OnFailure().

Doesn't look like it's strictly necessary, but suppresses the warning.

Review commit: https://reviewboard.mozilla.org/r/243918/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/243918/

Comment 2

[Jean-Yves Avenard [:jya]]

Comment on attachment 8975699 [details]
Bug 1461540 - Ensure errorMessage is initialized on all code paths in WebAudioDecodeJob::OnFailure().

https://reviewboard.mozilla.org/r/243918/#review250870

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ff5eea52d8da
Ensure errorMessage is initialized on all code paths in WebAudioDecodeJob::OnFailure(). r=jya

Comment 4

[Karl Tomlinson (:karlt)]

Comment on attachment 8975699 [details]
Bug 1461540 - Ensure errorMessage is initialized on all code paths in WebAudioDecodeJob::OnFailure().

https://reviewboard.mozilla.org/r/243918/#review250884

Prior to this change we would have a warning that would cause a CI error if
any ErrorCode enumeration value were not listed in this switch statement
e.g.

dom/media/webaudio/MediaBufferDecoder.cpp:564:11: warning: enumeration value 'NoAudio' not handled in switch [-Wswitch]

Adding a default to the switch statement defeats the -Wswitch warning, and so
adding a new enumerator to ErrorCode would no longer require adding a
coresponding case to this switch statement.

The -Wswitch warning seems useful to me, useful enough that I wouldn't disable
it for the sake of a notorious non-error warning that the compiler spits out
randomly.

Chris has checked that making the ErrorCode a scoped enumeration does not
suppress the warning.

For addressing the noise of the -Wmaybe-uninitialized, IMO the best solution
is to disable that warning globally, but that may be contentious.

This would also be an acceptable solution IMO:

const char* errorMessage = "MediaDecodeAudioDataUnknownError";

with the corresponding assignment in case UnknownError also removed.

Comment 5

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/ff5eea52d8da