Hello.
Does someone understand FF code (or libxpcom_glue usage) good enough to
comment on the following?
in nscore.h we define NS_COM_GLUE:
#ifdef MOZILLA_INTERNAL_API
# define NS_COM_GLUE
/*
The frozen string API has different definitions of nsAC?String
classes than the internal API. On systems that explicitly declare
dllexport symbols this is not a problem, but on ELF systems
internal symbols can accidentally "shine through"; we rename the
internal classes to avoid symbol conflicts.
*/
# define nsAString nsAString_internal
# define nsACString nsACString_internal
#else
# ifdef HAVE_VISIBILITY_ATTRIBUTE
# define NS_COM_GLUE NS_VISIBILITY_HIDDEN
# else
# define NS_COM_GLUE
# endif
#endif
And later while linking libxul.so, we link it to libxpcomglue_s.a with
"-z allextract" (as I understand - to make libxpcomglue_s.a symbols
available in libxul.so):
-Wl,-z -Wl,allextract
/export/home/alp/srcs/oi-userland/components/xulrunner/build/i86/dist/lib/libxpcomglue_s.a
-Wl,-z -Wl,defaultextract
so, definition in nsCategoryCache.h:
class NS_COM_GLUE nsCategoryObserver MOZ_FINAL : public nsIObserver {
public:
nsCategoryObserver(const char* aCategory,
nsCategoryListener* aCategoryListener);
~nsCategoryObserver();
void ListenerDied();
NS_DECL_ISUPPORTS
NS_DECL_NSIOBSERVER
private:
NS_HIDDEN_(void) RemoveObservers();
nsDataHashtable<nsCStringHashKey, nsCString> mHash;
nsCategoryListener* mListener;
nsCString mCategory;
bool mObserversRemoved;
};
causes this class to be hidden.
But it appears in object's headers
$ elfdump nsCategoryCache.o |grep nsCategoryObserver
Section Header[37]: sh_name: .data.rel.ro._ZTV18nsCategoryObserver
Section Header[38]: sh_name: .rel.data.rel.ro._ZTV18nsCategoryObserver
[5] 0x00000000 0x00000018 OBJT LOCL D 0 .data.rel.ro
_ZZN18nsCategoryObserver14QueryInterfaceERK4nsIDPPvE5table
[48] 0x00000000 0x0000000e FUNC GLOB H 0 .text
_ZN18nsCategoryObserver6AddRefEv
[49] 0x00000010 0x00000031 FUNC GLOB H 0 .text
_ZN18nsCategoryObserver14QueryInterfaceERK4nsIDPPv
[64] 0x00000050 0x000000d2 FUNC GLOB H 0 .text
_ZN18nsCategoryObserver15RemoveObserversEv
[68] 0x00000130 0x00000010 FUNC GLOB H 0 .text
_ZN18nsCategoryObserver12ListenerDiedEv
[69] 0x00000140 0x000003bd FUNC GLOB H 0 .text
_ZN18nsCategoryObserver7ObserveEP11nsISupportsPKcPKt
[87] 0x00000500 0x00000044 FUNC GLOB H 0 .text
_ZN18nsCategoryObserverD2Ev
[88] 0x00000000 0x00000018 OBJT WEAK H 0 .data.rel.ro._
_ZTV18nsCategoryObserver
[89] 0x00000500 0x00000044 FUNC GLOB H 0 .text
_ZN18nsCategoryObserverD1Ev
[90] 0x00000550 0x00000055 FUNC GLOB H 0 .text
_ZN18nsCategoryObserver7ReleaseEv
[96] 0x000005b0 0x0000056e FUNC GLOB H 0 .text
_ZN18nsCategoryObserverC2EPKcP18nsCategoryListener
[103] 0x000005b0 0x0000056e FUNC GLOB H 0 .text
_ZN18nsCategoryObserverC1EPKcP18nsCategoryListener
[0] [ COMDAT ] _ZTV18nsCategoryObserver
[1] .data.rel.ro._ZTV18nsCategoryObserver [37]
R_386_PC32 0x450 .rel.text
_ZN18nsCategoryObserver15RemoveObserversEv
R_386_GOTOFF 0x51c .rel.text
_ZTV18nsCategoryObserver
R_386_PC32 0x581 .rel.text
_ZN18nsCategoryObserverD1Ev
R_386_GOTOFF 0x5d0 .rel.text
_ZTV18nsCategoryObserver
R_386_PC32 0x13c .rel.text
_ZN18nsCategoryObserver15RemoveObserversEv
Relocation Section: .rel.data.rel.ro._ZTV18nsCategoryObserver
R_386_32 0x8 .rel.data.rel.
_ZN18nsCategoryObserver14QueryInterfaceERK4nsIDPPv
R_386_32 0xc .rel.data.rel.
_ZN18nsCategoryObserver6AddRefEv
R_386_32 0x10 .rel.data.rel.
_ZN18nsCategoryObserver7ReleaseEv
R_386_32 0x14 .rel.data.rel.
_ZN18nsCategoryObserver7ObserveEP11nsISupportsPKcPKt
And during linking this object is extracted from nsCategoryCache.o, this
results in
ld: fatal: relocation error: R_386_GOTOFF: file
../../dist/lib/libxpcomglue_s.a(nsCategoryCache.o): symbol vtable for
nsCategoryObserver: a GOT relative relocation must reference a local symbol
ld: fatal: relocation error: R_386_GOTOFF: file
../../dist/lib/libxpcomglue_s.a(nsCategoryCache.o): symbol vtable for
nsCategoryObserver: a GOT relative relocation must reference a local symbol
collect2: error: ld returned 1 exit status
make[4]: *** [libxul.so] Error 1
The main question is how and why this works with Sun CC and doesn't work
with GNU g++? What is the intention: to make all symbols public? How
this class nsCategoryObserver is used? Will defining it public do any harm?
--
Best regards,
Alexander Pyhalov,
system administrator of Computer Center of Southern Federal University
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