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c++: Make references to __cxa_pure_virtual weak.

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If a program has no other dependencies on libstdc++, we shouldn't require it
just for __cxa_pure_virtual, which is only there to give a prettier
diagnostic before crashing the program; resolving the reference to NULL will
also crash, just without the diagnostic.

gcc/cp/ChangeLog
2020-05-11  Jason Merrill  <jason@redhat.com>

	* decl.c (cxx_init_decl_processing): Call declare_weak for
	__cxa_pure_virtual.
This commit is contained in:
Jason Merrill 2020-05-11 14:05:46 -04:00
parent e5ccab839a
commit aa2c978400
3 changed files with 29 additions and 0 deletions
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5
gcc/cp/ChangeLog
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@ -1,3 +1,8 @@
2020-05-11 Jason Merrill <jason@redhat.com>
* decl.c (cxx_init_decl_processing): Call declare_weak for
__cxa_pure_virtual.
2020-05-11 Jason Merrill <jason@redhat.com>
* pt.c (instantiate_class_template_1): Call tsubst_expr for

3
gcc/cp/decl.c
View File

@ -4544,6 +4544,9 @@ cxx_init_decl_processing (void)
abort_fndecl
= build_library_fn_ptr ("__cxa_pure_virtual", void_ftype,
ECF_NORETURN | ECF_NOTHROW | ECF_COLD);
if (flag_weak)
/* If no definition is available, resolve references to NULL. */
declare_weak (abort_fndecl);
/* Perform other language dependent initializations. */
init_class_processing ();

21
gcc/testsuite/g++.dg/abi/pure-virtual1.C Normal file
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@ -0,0 +1,21 @@
// Test that we don't need libsupc++ just for __cxa_pure_virtual.
// { dg-do link }
// { dg-require-weak }
// { dg-additional-options "-fno-rtti -nodefaultlibs -lc" }
struct A
{
int i;
virtual void f() = 0;
A(): i(0) {}
};
struct B: A
{
virtual void f() {}
};
int main()
{
B b;
}