[Webkit-unassigned] [Bug 78513] New: If memset gets inlined at WebKit/Source/JavaScriptCore/wtf/Vector.h, it may produce a warning

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=78513

           Summary: If memset gets inlined at
                    WebKit/Source/JavaScriptCore/wtf/Vector.h, it may
                    produce a warning
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: asharif.tools at gmail.com


This warning happens in the following conditions:

1. If  chain of calls is inlined, including memset.
2. memset has a fill value of non-0, but a size of 0.
3. -D_FORTIFY_SOURCE=2 was passed.

This is the warning that I see when building Chrome.

In file included from /build/amd64-generic/usr/include/string.h:640:0,
                 from third_party/WebKit/Source/JavaScriptCore/wtf/FastAllocBase.h:90,
                 from third_party/WebKit/Source/JavaScriptCore/wtf/Vector.h:25,
                 from third_party/WebKit/Source/JavaScriptCore/wtf/text/StringImpl.h:31,
                 from third_party/WebKit/Source/JavaScriptCore/wtf/text/WTFString.h:29,
                 from third_party/WebKit/Source/WebCore/platform/text/PlatformString.h:28,
                 from third_party/WebKit/Source/WebCore/loader/cache/CachedResource.h:28,
                 from third_party/WebKit/Source/WebCore/loader/cache/CachedImage.h:26,
                 from third_party/WebKit/Source/WebCore/rendering/RenderObject.h:29,
                 from third_party/WebKit/Source/WebCore/rendering/RenderBoxModelObject.h:27,
                 from third_party/WebKit/Source/WebCore/rendering/RenderBox.h:26,
                 from third_party/WebKit/Source/WebCore/rendering/RenderFrameSet.h:26,
                 from third_party/WebKit/Source/WebCore/rendering/RenderFrameSet.cpp:25:
In function 'void* memset(void*, int, size_t)',
    inlined from 'WebCore::FrameEdgeInfo WebCore::RenderFrameSet::edgeInfo() const' at third_party/WebKit/Source/JavaScriptCore/wtf/Vector.h:184:13,
    inlined from 'void WebCore::RenderFrameSet::computeEdgeInfo()' at third_party/WebKit/Source/WebCore/rendering/RenderFrameSet.cpp:430:62:
/build/amd64-generic/usr/include/bits/string3.h:82:35: error: call to '__warn_memset_zero_len' declared with attribute warning: memset used with constant zero length parameter; this could be due to transposed parameters [-Werror]
cc1plus: all warnings being treated as errors

This can be fixed with the following patch:

diff --git a/Source/JavaScriptCore/wtf/Vector.h b/Source/JavaScriptCore/wtf/Vector.h
index 175f1a5..bf15998 100644
--- a/Source/JavaScriptCore/wtf/Vector.h
+++ b/Source/JavaScriptCore/wtf/Vector.h
@@ -181,7 +181,8 @@ namespace WTF {
        static void uninitializedFill(T* dst, T* dstEnd, const T& val)
        {
            ASSERT(sizeof(T) == sizeof(char));
-            memset(dst, val, dstEnd - dst);
+            if (dstEnd - dst)
+              memset(dst, val, dstEnd - dst);
        }
    };

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