1159131 - dom/canvas/compiledtest/../WebGLElementArrayCache.cpp:245:10: error: 'newBound' may be used uninitialized in this function [-Wuninitialized]

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, defect)

Description

[Chris Peterson [:cpeterson]]

Attachment: Wuninitialized_newBound.patch

This patch moves the UpdateUpperBound() function's `out_upperBound` parameter to a local variable to work around a false positive -Wuninitialized gcc warning about std::max() template function's arguments in DEBUG PGO builds. PGO opt builds are not affected. The false positive warning is actually about UpdateUpperBound()'s `newBound` variable, not `out_upperBound`, but dereferencing the out_upperBound pointer into a local variable seems less silly than duplicating the newBound parameter into a local variable like `uint32_t newBound2 = newBound` (which also works around the false positive warning).

Why accept this silly workaround for a false positive warning? Because it's the last -Wuninitialized warning in mozilla-central and will allow me to land bug 1001975, removing -Wuninitialized from the warnings exempted from FAIL_ON_WARNINGS warnings-as-errors. gcc's -Wuninitialized has a well-deserved reputation for reporting false positives, but gcc 4.7 (mozilla-central's current minimum gcc version) separated -Wuninitialized's less reliable checks into a new and unreliable -Wmaybe-uninitialized warning. -Wuninitialized warnings are rarely false positives these days.

This patch also changes some (unrelated) MOZ_ASSERTs to MOZ_RELEASE_ASSERTs in the TestWebGLElementArrayCache.cpp file that triggered this -Wuninitialized warning.

https://treeherder.mozilla.org/#/jobs?repo=try&revision=05dd713f8de1

/builds/slave/try-l64-d-00000000000000000000/build/src/dom/canvas/compiledtest/../WebGLElementArrayCache.cpp:245:10: error: 'newBound' may be used uninitialized in this function [-Werror=uninitialized]
/builds/slave/try-l64-d-00000000000000000000/build/src/dom/canvas/compiledtest/../WebGLElementArrayCache.cpp:245:10: error: 'newBound' may be used uninitialized in this function [-Werror=uninitialized]
/builds/slave/try-l64-d-00000000000000000000/build/src/dom/canvas/compiledtest/../WebGLElementArrayCache.cpp:245:10: error: 'newBound' may be used uninitialized in this function [-Werror=uninitialized]
/builds/slave/try-l64-d-00000000000000000000/build/src/dom/canvas/compiledtest/../WebGLElementArrayCache.cpp:245:10: error: 'newBound' may be used uninitialized in this function [-Werror=uninitialized]
/builds/slave/try-l64-d-00000000000000000000/build/src/dom/canvas/compiledtest/../WebGLElementArrayCache.cpp:245:10: error: 'newBound' may be used uninitialized in this function [-Werror=uninitialized]
/builds/slave/try-l64-d-00000000000000000000/build/src/dom/canvas/compiledtest/../WebGLElementArrayCache.cpp:245:10: error: 'newBound' may be used uninitialized in this function [-Werror=uninitialized]

Comment 1

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/7b6a610e26b9

Comment 2

[Chris Peterson [:cpeterson]]

Thanks!

https://hg.mozilla.org/integration/mozilla-inbound/rev/7b6a610e26b9

Comment 3

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/7b6a610e26b9