| Message ID | 33F6DDD7-3914-4A04-9F43-0411A46A206E@sandoe.co.uk |
|---|---|
| State | New |
| Headers | show |
| Series | [Darwin] Fix build warnings for libstdc++ [NFC] | expand |
On 03/12/18 00:37 +0000, Iain Sandoe wrote: >Hi, > >GCC does not export construction vtable symbols from shared libraries**. > >The symbols are marked hidden in the objects; for Darwin that makes them also external (“private_extern” is Darwin’s hidden) which means that they show up in the list of possible symbols for export from libstdc++, and there are sufficiently relaxed match conditions that they reach the exports list. When Darwin’s static linker encounters them it generates a warning that they cannot be exported. This patch prunes them from the list of symbols to be considered, thus eliminating the warnings. > >OK for trunk? Yes, OK. >Iain > >** This seems a design decision, rather than an ABI mandate - note that, on Darwin at least, these symbols *are* visible in libc++. > >libstdc++-v3/ > > * scripts/make_exports.pl (check names): Don’t try to export construction > vtable symbols. > > >diff --git a/libstdc++-v3/scripts/make_exports.pl b/libstdc++-v3/scripts/make_exports.pl >index 7c9e4e31d4..93100e17dd 100644 >--- a/libstdc++-v3/scripts/make_exports.pl >+++ b/libstdc++-v3/scripts/make_exports.pl >@@ -103,6 +103,14 @@ NAME: while (<NM>) { > # Ignore undefined and local symbols. > next if (/^([^ ]+) [Ua-z] /); > >+ # GCC does not export construction vtables from shared libraries. >+ # However the symbols are marked hidden, for Darwin that makes them >+ # also external "private_extern", which means that they show up in >+ # this list. When ld64 encounters them it generates a warning that >+ # they cannot be exported, so trim them from the set now. >+ next if (/^construction vtable.*$/); >+ next if (/^__ZTC.*$/); >+ >
diff --git a/libstdc++-v3/scripts/make_exports.pl b/libstdc++-v3/scripts/make_exports.pl index 7c9e4e31d4..93100e17dd 100644 --- a/libstdc++-v3/scripts/make_exports.pl +++ b/libstdc++-v3/scripts/make_exports.pl @@ -103,6 +103,14 @@ NAME: while (<NM>) { # Ignore undefined and local symbols. next if (/^([^ ]+) [Ua-z] /); + # GCC does not export construction vtables from shared libraries. + # However the symbols are marked hidden, for Darwin that makes them + # also external "private_extern", which means that they show up in + # this list. When ld64 encounters them it generates a warning that + # they cannot be exported, so trim them from the set now. + next if (/^construction vtable.*$/); + next if (/^__ZTC.*$/); +