Prepare for forthcoming LLVM 13 API change.

macdice · macdice · commit 9b4e4cfe66ff · 2021-06-25T11:28:20.000+12:00
LLVM 13 (due out in September) has changed the semantics of LLVMOrcAbsoluteSymbols(), so we need to bump some reference counts to avoid a double-free that causes crashes and bad query results. A proactive change seems necessary to avoid having a window of time where our respective latest releases would interact badly. It's possible that the situation could change before then, though. Thanks to Fabien Coelho for monitoring bleeding edge LLVM and Andres Freund for tracking down the change. Back-patch to 11, where the JIT code arrived. Discussion: https://postgr.es/m/CA%2BhUKGLEy8mgtN7BNp0ooFAjUedDTJj5dME7NxLU-m91b85siA%40mail.gmail.com
diff --git a/src/backend/jit/llvm/llvmjit.c b/src/backend/jit/llvm/llvmjit.c
@@ -1106,6 +1106,9 @@ llvm_resolve_symbols(LLVMOrcDefinitionGeneratorRef GeneratorObj, void *Ctx,
 	{
 		const char *name = LLVMOrcSymbolStringPoolEntryStr(LookupSet[i].Name);
 
+#if LLVM_VERSION_MAJOR > 12
+		LLVMOrcRetainSymbolStringPoolEntry(LookupSet[i].Name);
+#endif
 		symbols[i].Name = LookupSet[i].Name;
 		symbols[i].Sym.Address = llvm_resolve_symbol(name, NULL);
 		symbols[i].Sym.Flags.GenericFlags = LLVMJITSymbolGenericFlagsExported;

Original file line number	Diff line number	Diff line change
`@@ -1106,6 +1106,9 @@ llvm_resolve_symbols(LLVMOrcDefinitionGeneratorRef GeneratorObj, void *Ctx,`
`1106`	`1106`	`{`
`1107`	`1107`	`const char *name = LLVMOrcSymbolStringPoolEntryStr(LookupSet[i].Name);`
`1108`	`1108`
	`1109`	`+#if LLVM_VERSION_MAJOR > 12`
	`1110`	`+ LLVMOrcRetainSymbolStringPoolEntry(LookupSet[i].Name);`
	`1111`	`+#endif`
`1109`	`1112`	`symbols[i].Name = LookupSet[i].Name;`
`1110`	`1113`	`symbols[i].Sym.Address = llvm_resolve_symbol(name, NULL);`
`1111`	`1114`	`symbols[i].Sym.Flags.GenericFlags = LLVMJITSymbolGenericFlagsExported;`