[RFC] Dealing with ODR violations in GCC

[Jan Hubicka]

> Hello.
> 
> I've just finished successfully chromium LTO build and there's list of mainly -Wodr warnings.
> I think some of them are false positives?

What of those you consider to be false?
I wonder if we can print just type name so we avoid using the wrong "struct" in place of class...
> 
> Thanks,
> Martin

> ../../third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h:295:0: warning: type ???struct WebCryptoEcKeyImportParams??? violates one definition rule [-Wodr]
>  class WebCryptoEcKeyImportParams : public WebCryptoAlgorithmParams {
>  ^
> ../../third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h:295:0: note: a different type is defined in another translation unit
>  class WebCryptoEcKeyImportParams : public WebCryptoAlgorithmParams {
>  ^
> ../../third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h:307:0: note: the first difference of corresponding definitions is field ???m_namedCurve???
>      const WebCryptoNamedCurve m_namedCurve;
>  ^
> ../../third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h:295:0: note: a field of same name but different type is defined in another translation unit
>  class WebCryptoEcKeyImportParams : public WebCryptoAlgorithmParams {
>  ^

The line info seems wrong here though.
> ../../third_party/icu/source/common/unicode/bytestream.h:48:0: note: virtual method ???_ZTIN6icu_528ByteSinkE???
>  class U_COMMON_API ByteSink : public UMemory {
>  ^
> <built-in>: note: ought to match virtual method ???__cxa_pure_virtual??? but does not

This message also should be sanitized - we probably want to special case cxa_pure_virtual...

Honza
> In function ???__fread_alias???,
>     inlined from ???_ZN21SafeBrowsingStoreFile13CheckValidityEv.part.41.constprop??? at ../../chrome/browser/safe_browsing/safe_browsing_store_file.cc:611:0:
> /usr/include/bits/stdio2.h:290:0: warning: call to ???__fread_chk_warn??? declared with attribute warning: fread called with bigger size * nmemb than length of destination buffer
>   return __fread_chk (__ptr, __bos0 (__ptr), __size, __n, __stream);
>  ^
> /usr/include/bits/stdio2.h:290:0: warning: call to ???__fread_chk_warn??? declared with attribute warning: fread called with bigger size * nmemb than length of destination buffer
> In function ???__read_alias???,
>     inlined from ???GetAppOutputInternal.constprop??? at ../../base/process/launch_posix.cc:613:0:
> /usr/include/bits/unistd.h:39:0: warning: call to ???__read_chk_warn??? declared with attribute warning: read called with bigger length than size of the destination buffer
>   return __read_chk (__fd, __buf, __nbytes, __bos0 (__buf));
>  ^
>