25864 2009-05-19 09:10:08 -0700 strict aliasing issues in WebCore/page/SecurityOriginHash.h 2009-05-19 22:45:42 -0700 1 1 1 Unclassified WebKit WebCore Misc. 528+ (Nightly build) PC Linux RESOLVED WONTFIX P2 Normal --- 0 craig.schlenter webkit-unassigned oldest_to_newest 121916 0 craig.schlenter 2009-05-19 09:10:08 -0700 I've been compiling chromium with gcc 4.4 and I've had to use -fno-strict-aliasing for webkit due to a couple of issues. The code in question should be equivalent to that in WebKit itself. Here's one of the issues: In file included from /home/craig/chromium.git/src/third_party/WebKit/WebCore/storage/OriginQuotaManager.h:35, from /home/craig/chromium.git/src/third_party/WebKit/WebCore/storage/DatabaseTracker.cpp:40: /home/craig/chromium.git/src/third_party/WebKit/WebCore/platform/text/StringImpl.h: In static member function 'static unsigned int WebCore::SecurityOriginHash::hash(WebCore::SecurityOrigin*)': /home/craig/chromium.git/src/third_party/WebKit/WebCore/platform/text/StringImpl.h:210: warning: dereferencing pointer 'data' does break strict-aliasing rules /home/craig/chromium.git/src/third_party/WebKit/WebCore/page/SecurityOriginHash.h:46: note: initialized from here /home/craig/chromium.git/src/third_party/WebKit/WebCore/platform/text/StringImpl.h:213: note: initialized from here /home/craig/chromium.git/src/third_party/WebKit/WebCore/platform/text/StringImpl.h:211: warning: dereferencing pointer '<anonymous>' does break strict-aliasing rules /home/craig/chromium.git/src/third_party/WebKit/WebCore/platform/text/StringImpl.h:211: note: initialized from here I'm attaching a patch which seems to work for me but I have only tested it on linux ... I don't know how other compilers will deal with the union initialisation etc. etc. 121917 1 30472 craig.schlenter 2009-05-19 09:12:43 -0700 Created attachment 30472 attempted fix for strict aliasing issue only tested on linux with gcc 4.4 in chromium 121923 2 30472 darin 2009-05-19 09:30:18 -0700 Comment on attachment 30472 attempted fix for strict aliasing issue In the past, WebCore has not been compiled with strict aliasing turned on. Unlike JavaScriptCore, where we fixed all the strict aliasing issues. I would expect many, many problems in WebCore. Not just warnings, but actual code generation problems. Do we really want to do this project (turning on strict aliasing in WebCore)? 121932 3 evan 2009-05-19 10:06:44 -0700 I take Darin's comment to mean that in the interim, we should turn off strict aliasing in Chrome for now. 121940 4 pkasting 2009-05-19 11:06:27 -0700 Over time we should definitely fix strict aliasing problems. GCC is not the only compiler where they can cause issues. Generally they are easy to fix by adding unions (I would probably elect to use more typedefs in the particular patch above for clarity, though). 122069 5 30472 eric 2009-05-19 22:45:08 -0700 Comment on attachment 30472 attempted fix for strict aliasing issue bug 16317 is another way to make this code cleaner. But given the above comments, I think we should close this and someone who is interested in turning on strict aliasing warnings for WebCore can do this for real later. 122070 6 eric 2009-05-19 22:45:42 -0700 WONTFIX based on the above comments. Feel free to open a more general bug about turning on strict aliasing in WebCore. 30472 2009-05-19 09:12:43 -0700 2009-05-19 22:45:08 -0700 attempted fix for strict aliasing issue securityoriginhash.patch text/plain 1686 craig.schlenter SW5kZXg6IFdlYkNvcmUvQ2hhbmdlTG9nCj09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT0KLS0tIFdlYkNvcmUvQ2hhbmdlTG9n CShyZXZpc2lvbiA0Mzg1OCkKKysrIFdlYkNvcmUvQ2hhbmdlTG9nCSh3b3JraW5nIGNvcHkpCkBA IC0xLDMgKzEsMTMgQEAKKzIwMDktMDUtMTkgIENyYWlnIFNjaGxlbnRlciAgPGNyYWlnLnNjaGxl bnRlckBnbWFpbC5jb20+CisKKyAgICAgICAgUmV2aWV3ZWQgYnkgTk9CT0RZIChPT1BTISkuCisK KyAgICAgICAgU3F1YXNoIGdjYyA0LjQgc3RyaWN0IGFsaWFzaW5nIHByb2JsZW1zIGluIFNlY3Vy aXR5T3JpZ2luSGFzaC5oCisgICAgICAgIGJ5IHVzaW5nIGEgdW5pb24gdG8gImNhc3QiIGJldHdl ZW4gdHlwZXMuCisKKyAgICAgICAgKiBwYWdlL1NlY3VyaXR5T3JpZ2luSGFzaC5oOgorICAgICAg ICAoV2ViQ29yZTo6U2VjdXJpdHlPcmlnaW5IYXNoOjpoYXNoKToKKwogMjAwOS0wNS0xOSAgS2Vu bmV0aCBSb2hkZSBDaHJpc3RpYW5zZW4gIDxrZW5uZXRoLmNocmlzdGlhbnNlbkBvcGVuYm9zc2Eu b3JnPgogCiAgICAgICAgIFJldmlld2VkIGJ5IEFyaXlhIEhpZGF5YXQuCkluZGV4OiBXZWJDb3Jl L3BhZ2UvU2VjdXJpdHlPcmlnaW5IYXNoLmgKPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PQotLS0gV2ViQ29yZS9wYWdlL1Nl Y3VyaXR5T3JpZ2luSGFzaC5oCShyZXZpc2lvbiA0Mzg1OCkKKysrIFdlYkNvcmUvcGFnZS9TZWN1 cml0eU9yaWdpbkhhc2guaAkod29ya2luZyBjb3B5KQpAQCAtMzgsMTIgKzM4LDE2IEBAIG5hbWVz cGFjZSBXZWJDb3JlIHsKIHN0cnVjdCBTZWN1cml0eU9yaWdpbkhhc2ggewogICAgIHN0YXRpYyB1 bnNpZ25lZCBoYXNoKFNlY3VyaXR5T3JpZ2luKiBvcmlnaW4pCiAgICAgewotICAgICAgICB1bnNp Z25lZCBoYXNoQ29kZXNbM10gPSB7CisgICAgICAgIC8vIFRoaXMgaXMgcGFpbmZ1bCBidXQgaXQg YXZvaWRzIGdjYyA0LjQgc3RyaWN0IGFsaWFzaW5nIGlzc3Vlcy4KKyAgICAgICAgdW5pb24gewor ICAgICAgICAgICAgdW5zaWduZWQgdVszXTsKKyAgICAgICAgICAgIFVDaGFyIHVjWygzICogc2l6 ZW9mKHVuc2lnbmVkKSkvc2l6ZW9mKFVDaGFyKV07CisgICAgICAgIH0gaGFzaENvZGVzID0ge3sK ICAgICAgICAgICAgIG9yaWdpbi0+cHJvdG9jb2woKS5pbXBsKCkgPyBvcmlnaW4tPnByb3RvY29s KCkuaW1wbCgpLT5oYXNoKCkgOiAwLAogICAgICAgICAgICAgb3JpZ2luLT5ob3N0KCkuaW1wbCgp ID8gb3JpZ2luLT5ob3N0KCkuaW1wbCgpLT5oYXNoKCkgOiAwLAogICAgICAgICAgICAgb3JpZ2lu LT5wb3J0KCkKLSAgICAgICAgfTsKLSAgICAgICAgcmV0dXJuIFN0cmluZ0ltcGw6OmNvbXB1dGVI YXNoKHJlaW50ZXJwcmV0X2Nhc3Q8VUNoYXIqPihoYXNoQ29kZXMpLCBzaXplb2YoaGFzaENvZGVz KSAvIHNpemVvZihVQ2hhcikpOworICAgICAgICB9fTsKKyAgICAgICAgcmV0dXJuIFN0cmluZ0lt cGw6OmNvbXB1dGVIYXNoKGhhc2hDb2Rlcy51Yywgc2l6ZW9mKGhhc2hDb2Rlcy51YykgLyBzaXpl b2YoVUNoYXIpKTsKICAgICB9CiAgICAgc3RhdGljIHVuc2lnbmVkIGhhc2goY29uc3QgUmVmUHRy PFNlY3VyaXR5T3JpZ2luPiYgb3JpZ2luKQogICAgIHsK