[Webkit-unassigned] [Bug 226643] New: -Wnonnull warning in JITCall.cpp

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=226643

            Bug ID: 226643
           Summary: -Wnonnull warning in JITCall.cpp
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: mcatanzaro at gnome.org

[3/3414] Building CXX object Source/JavaScriptCore/CMakeF...vedSources/unified-sources/UnifiedSource-3a3c4ec0-3.cpp.o
In file included from JavaScriptCore/DerivedSources/unified-sources/UnifiedSource-3a3c4ec0-3.cpp:7:
../../Source/JavaScriptCore/jit/JITCall.cpp: In member function ‘void JSC::JIT::compileOpCall(const JSC::Instruction*, unsigned int) [with Op = JSC::OpCallEval]’:
../../Source/JavaScriptCore/jit/JITCall.cpp:256:10: warning: ‘this’ pointer is null [-Wnonnull]
  256 |     auto slowPaths = info->emitFastPath(*this, regT0, regT2, CallLinkInfo::UseDataIC::Yes);
      |          ^~~~~~~~~
In file included from ../../Source/JavaScriptCore/bytecode/CodeBlock.h:34,
                 from ../../Source/JavaScriptCore/jit/AssemblyHelpers.h:30,
                 from ../../Source/JavaScriptCore/jit/CCallHelpers.h:30,
                 from ../../Source/JavaScriptCore/jit/JITAddGenerator.h:30,
                 from ../../Source/JavaScriptCore/jit/JITAddGenerator.cpp:27,
                 from JavaScriptCore/DerivedSources/unified-sources/UnifiedSource-3a3c4ec0-3.cpp:1:
../../Source/JavaScriptCore/bytecode/CallLinkInfo.h:178:30: note: in a call to non-static member function ‘JSC::AbstractMacroAssembler<JSC::X86Assembler>::JumpList JSC::CallLinkInfo::emitFastPath(JSC::CCallHelpers&, JSC::GPRReg, JSC::GPRReg, JSC::CallLinkInfo::UseDataIC)’
  178 |     MacroAssembler::JumpList emitFastPath(CCallHelpers&, GPRReg calleeGPR, GPRReg callLinkInfoGPR, UseDataIC) WARN_UNUSED_RETURN;
      |                              ^~~~~~~~~~~~

Despite the very misleading text of the warning, GCC is concerned that *info* may be NULL at JITCall.cpp:256. (It's concerned about the value of 'this' *inside* the call to info->emitFastPath.) Would be great if a JavaScriptCore developer could investigate it, please. From my amateurish read of the code, it sure *looks* like GCC's warning is reasonable as there appear to be codepaths where info is NULL at that point.

The warning may be suppressed either with IGNORE_WARNINGS_BEGIN/END or by adding a RELEASE_ASSERT(info).

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