| Message ID | 20110122175448.GC8959@kam.mff.cuni.cz |
|---|---|
| State | New |
| Headers | show |
On Sat, Jan 22, 2011 at 6:54 PM, Jan Hubicka <hubicka@ucw.cz> wrote: > Hi, this PR is about fact that we no longer output > "weak declaration must precede definition" errors. These errors > makes no sense in unit-at-a-time compilation model and thus they > didn't exist since we dropped non-unit-at-a-time. > > This patch updates docs and turns the error messages into sanity check. > We might document the behaviour change, but I don't think we need > to preserve this limitation of earlier compilers. > > Bootstrapped/regtested x86_64-linux, OK? Ok. Thanks, Richard. > Honza > > PR c/21659 > * doc/extend.texi (weak pragma): Drop claim that it must > appear before definition. > * varasm.c (merge_weak, declare_weak): Only sanity check > that DECL is not output at a time it is declared weak. > > Index: doc/extend.texi > =================================================================== > --- doc/extend.texi (revision 169127) > +++ doc/extend.texi (working copy) > @@ -13024,8 +13024,7 @@ aliases. > @cindex pragma, weak > This pragma declares @var{symbol} to be weak, as if the declaration > had the attribute of the same name. The pragma may appear before > -or after the declaration of @var{symbol}, but must appear before > -either its first use or its definition. It is not an error for > +or after the declaration of @var{symbol}. It is not an error for > @var{symbol} to never be defined at all. > > @item #pragma weak @var{symbol1} = @var{symbol2} > Index: varasm.c > =================================================================== > --- varasm.c (revision 169127) > +++ varasm.c (working copy) > @@ -5139,20 +5139,16 @@ merge_weak (tree newdecl, tree olddecl) > /* NEWDECL is weak, but OLDDECL is not. */ > > /* If we already output the OLDDECL, we're in trouble; we can't > - go back and make it weak. This error cannot be caught in > - declare_weak because the NEWDECL and OLDDECL was not yet > - been merged; therefore, TREE_ASM_WRITTEN was not set. */ > - if (TREE_ASM_WRITTEN (olddecl)) > - error ("weak declaration of %q+D must precede definition", > - newdecl); > + go back and make it weak. This should never happen in > + unit-at-a-time compilation. */ > + gcc_assert (!TREE_ASM_WRITTEN (olddecl)); > > /* If we've already generated rtl referencing OLDDECL, we may > have done so in a way that will not function properly with > - a weak symbol. */ > - else if (TREE_USED (olddecl) > - && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (olddecl))) > - warning (0, "weak declaration of %q+D after first use results " > - "in unspecified behavior", newdecl); > + a weak symbol. Again in unit-at-a-time this should be > + impossible. */ > + gcc_assert (!TREE_USED (olddecl) > + || !TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (olddecl))); > > if (TARGET_SUPPORTS_WEAK) > { > @@ -5184,10 +5180,9 @@ merge_weak (tree newdecl, tree olddecl) > void > declare_weak (tree decl) > { > + gcc_assert (TREE_CODE (decl) != FUNCTION_DECL || !TREE_ASM_WRITTEN (decl)); > if (! TREE_PUBLIC (decl)) > error ("weak declaration of %q+D must be public", decl); > - else if (TREE_CODE (decl) == FUNCTION_DECL && TREE_ASM_WRITTEN (decl)) > - error ("weak declaration of %q+D must precede definition", decl); > else if (!TARGET_SUPPORTS_WEAK) > warning (0, "weak declaration of %q+D not supported", decl); > >
Index: doc/extend.texi =================================================================== --- doc/extend.texi (revision 169127) +++ doc/extend.texi (working copy) @@ -13024,8 +13024,7 @@ aliases. @cindex pragma, weak This pragma declares @var{symbol} to be weak, as if the declaration had the attribute of the same name. The pragma may appear before -or after the declaration of @var{symbol}, but must appear before -either its first use or its definition. It is not an error for +or after the declaration of @var{symbol}. It is not an error for @var{symbol} to never be defined at all. @item #pragma weak @var{symbol1} = @var{symbol2} Index: varasm.c =================================================================== --- varasm.c (revision 169127) +++ varasm.c (working copy) @@ -5139,20 +5139,16 @@ merge_weak (tree newdecl, tree olddecl) /* NEWDECL is weak, but OLDDECL is not. */ /* If we already output the OLDDECL, we're in trouble; we can't - go back and make it weak. This error cannot be caught in - declare_weak because the NEWDECL and OLDDECL was not yet - been merged; therefore, TREE_ASM_WRITTEN was not set. */ - if (TREE_ASM_WRITTEN (olddecl)) - error ("weak declaration of %q+D must precede definition", - newdecl); + go back and make it weak. This should never happen in + unit-at-a-time compilation. */ + gcc_assert (!TREE_ASM_WRITTEN (olddecl)); /* If we've already generated rtl referencing OLDDECL, we may have done so in a way that will not function properly with - a weak symbol. */ - else if (TREE_USED (olddecl) - && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (olddecl))) - warning (0, "weak declaration of %q+D after first use results " - "in unspecified behavior", newdecl); + a weak symbol. Again in unit-at-a-time this should be + impossible. */ + gcc_assert (!TREE_USED (olddecl) + || !TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (olddecl))); if (TARGET_SUPPORTS_WEAK) { @@ -5184,10 +5180,9 @@ merge_weak (tree newdecl, tree olddecl) void declare_weak (tree decl) { + gcc_assert (TREE_CODE (decl) != FUNCTION_DECL || !TREE_ASM_WRITTEN (decl)); if (! TREE_PUBLIC (decl)) error ("weak declaration of %q+D must be public", decl); - else if (TREE_CODE (decl) == FUNCTION_DECL && TREE_ASM_WRITTEN (decl)) - error ("weak declaration of %q+D must precede definition", decl); else if (!TARGET_SUPPORTS_WEAK) warning (0, "weak declaration of %q+D not supported", decl);