Last good https://build.chromium.org/p/chromium.fyi/builders/CrWinClang%28dbg%29%20tester/builds/3799
First bad https://build.chromium.org/p/chromium.fyi/builders/CrWinClang%28dbg%29%20tester/builds/3800

(not caused by the clang roll)


Also on 64-bit
Last "good" https://build.chromium.org/p/chromium.fyi/builders/CrWinClang64%28dbg%29%20tester/builds/1273
First bad https://build.chromium.org/p/chromium.fyi/builders/CrWinClang64%28dbg%29%20tester/builds/1275


Example failure:

DevToolsAgentTest.DevToolsResumeOnClose (run #1):
[ RUN      ] DevToolsAgentTest.DevToolsResumeOnClose
[3232:4560:0314/180426:38571372:WARNING:resource_bundle.cc(307)] locale_file_path.empty() for locale


#
# Fatal error in ../../v8/src/api.cc, line 166
# Check failed: handle_scope_implementer->GetMicrotasksScopeDepth() || !handle_scope_implementer->DebugMicrotasksScopeDepthIsZero().
#
Backtrace:
	(No symbol) [0x0000000000000000]
	std::vector<v8::CpuProfileDeoptFrame,std::allocator<v8::CpuProfileDeoptFrame> >::_Reallocate [0x0000000001E58AC7+17587049]
	std::vector<v8::CpuProfileDeoptFrame,std::allocator<v8::CpuProfileDeoptFrame> >::_Reallocate [0x0000000001E51725+17557447]
	std::vector<v8::CpuProfileDeoptFrame,std::allocator<v8::CpuProfileDeoptFrame> >::_Reallocate [0x0000000000E4FFDF+774273]
	std::vector<v8::CpuProfileDeoptFrame,std::allocator<v8::CpuProfileDeoptFrame> >::_Reallocate [0x0000000000DF34DF+394625]
	std::vector<v8::CpuProfileDeoptFrame,std::allocator<v8::CpuProfileDeoptFrame> >::_Reallocate [0x0000000000E22B97+588857]
	blink::KURL::operator new [0x000000000F43A60C+6594091]
	blink::KURL::operator new [0x000000000F439EAB+6592202]
	blink::KURL::operator new [0x000000000F410303+6421282]
	blink::KURL::operator new [0x000000000F41039F+6421438]
	blink::InspectorDebuggerAgent::enable [0x0000000011843678+72]
	blink::PageDebuggerAgent::enable [0x00000000118E8DCF+223]
	blink::KURL::operator new [0x000000000F505C7D+7427228]
	blink::KURL::operator new [0x000000000F5359C9+7623144]
	blink::WebLocalFrameImpl::activeMatchFrame [0x00000000100FA42B+1013197]
	blink::WebLocalFrameImpl::activeMatchFrame [0x00000000100FA09A+1012284]
	content::DevToolsAgentHost::GetOrCreateFor [0x000000000C2E8774+58581791]


The 64-bit build has a v8 roll in the regression range, but the 32-bit one doesn't.


They both have https://codereview.chromium.org/1769273004 so it might be that. (dgozman: This might be a compiler bug, so FYI only for now.)



This is fairly similar to  bug 590086  (which I think in the end was caused by a large alloca?), but it's in debug not in release, and it's both 64-bit and 32-bit -- so maybe it's something completely different.