Bug 7812 – Segfault on invalid code during template match deduction with errors gagged

The following snippet compiles fine using 2.058, but segfaults with latest Git master (c2824d43): --- template A(T...) { } template B(alias C) if (C) { } template D() { alias B!(A!(NonExistent!())) D; } static assert(!__traits(compiles, D!())); --- --- Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_PROTECTION_FAILURE at address: 0x00000000 0x000cf64d in DsymbolExp::semantic (this=0x4631e0, sc=0x462c30) at expression.c:2920 2920 s = ti->inst->toAlias(); (gdb) bt #0 0x000cf64d in DsymbolExp::semantic (this=0x4631e0, sc=0x462c30) at expression.c:2920 #1 0x000cde68 in IdentifierExp::semantic (this=0x4631c0, sc=0x462c30) at expression.c:2635 #2 0x001c43c9 in TemplateDeclaration::matchWithInstance (this=0x426ab0, ti=0x462010, dedtypes=0xbfffec88, fargs=0x0, flag=0) at template.c:790 #3 0x001d1208 in TemplateInstance::findBestMatch (this=0x462010, sc=0x461d50, fargs=0x0) at template.c:5152 #4 0x001c88f1 in TemplateInstance::semantic (this=0x462010, sc=0x461d50, fargs=0x0) at template.c:4468 #5 0x001d07a4 in TemplateInstance::semantic (this=0x462010, sc=0x461d50) at template.c:4321 #6 0x00166845 in TypeInstance::resolve (this=0x461fb0, loc={filename = 0x426710 "test.d", linnum= 8}, sc=0x461d50, pe=0xbfffef18, pt=0xbfffef1c, ps=0xbfffef14) at mtype.c:6690 #7 0x00166bcc in TypeInstance::toDsymbol (this=0x461fb0, sc=0x461d50) at mtype.c:6745 #8 0x00092118 in AliasDeclaration::semantic (this=0x461f50, sc=0x461d50) at declaration.c:461 #9 0x001d086a in TemplateInstance::expandMembers (this=0x4271a0, sc2=0x461d50) at template.c:4338 #10 0x001d090e in TemplateInstance::tryExpandMembers (this=0x4271a0, sc2=0x461d50) at template.c:4374 #11 0x001c9265 in TemplateInstance::semantic (this=0x4271a0, sc=0x461bb0, fargs=0x0) at template.c:4736 #12 0x001d07a4 in TemplateInstance::semantic (this=0x4271a0, sc=0x461bb0) at template.c:4321 #13 0x00166845 in TypeInstance::resolve (this=0x427250, loc={filename = 0x426710 "test.d", linnum = 11}, sc=0x461bb0, pe=0xbffff44c, pt=0xbffff43c, ps=0xbffff438) at mtype.c:6690 #14 0x00214d1f in TraitsExp::semantic (this=0x4272b0, sc=0x461bb0) at traits.c:462 #15 0x000db61d in UnaExp::semantic (this=0x4272d0, sc=0x461bb0) at expression.c:5828 #16 0x000e85c3 in NotExp::semantic (this=0x4272d0, sc=0x461bb0) at expression.c:8503 #17 0x001e5af7 in StaticAssert::semantic2 (this=0x4272f0, sc=0x461bb0) at staticassert.c:59 #18 0x0014e187 in Module::semantic2 (this=0x4265f0) at module.c:840 #19 0x0014a553 in tryMain (argc=5, argv=0x41fea0) at mars.c:1301 #20 0x0014b282 in main (argc=2, argv=0xbffffbd8) at mars.c:1476 --- This has likely been uncovered by the change from issue 7481.

Thanks for your good stack trace. https://github.com/D-Programming-Language/dmd/pull/859

Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/16b2ccfc2fec8a85891a0c3275d0f94653b58970 Merge pull request #859 from 9rnsr/fix7812 Issue 7812 - Segfault on invalid code during template match deduction with errors gagged