[Lldb-commits] [PATCH] D78972: Treat hasWeakODRLinkage symbols as external in REPL computations

Jim Ingham via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Mon Apr 27 17:16:46 PDT 2020

jingham created this revision.
jingham added a reviewer: JDevlieghere.
jingham added a project: LLDB.
Herald added a subscriber: lldb-commits.

The way both the REPL and the --top-level mode of the expression parser work is that they compile and JIT the code the user provided, and then look through the resultant IR and find any llvm::Functions produced by the compilation.  Then it iterates over those functions and if they are marked "external", it adds them to a table of functions that it then makes available to subsequent expressions.

The test we were using for "is external" was hasExternalLinkage || hasLinkOnceODRLinkage.  However, there's a third form of external function: hasWeakODRLinkage that can sometimes be produced, which is also intended to be an exported symbol.  This  patch just includes that predicate to the test we were doing.

I don't have a way to write a C-based test for this as I don't know how to craft a user expression in C that will make such a thing.  I asked around a bit and nobody had an easy way to do this.

OTOH, the swift compiler uses this linkage type when it makes the "default argument provider" for a function with default arguments.  So I can easily write a swift REPL test for this.  But if somebody knows how to make a C function in the lldb expression parser with a WeakODRLinkage, show me and I'll happily add a test for it here.

  rG LLVM Github Monorepo



Index: lldb/source/Expression/IRExecutionUnit.cpp
--- lldb/source/Expression/IRExecutionUnit.cpp
+++ lldb/source/Expression/IRExecutionUnit.cpp
@@ -331,7 +331,8 @@
     const bool external =
-        function.hasExternalLinkage() || function.hasLinkOnceODRLinkage();
+        function.hasExternalLinkage() || function.hasLinkOnceODRLinkage()
+        || function.hasWeakODRLinkage();
     void *fun_ptr = m_execution_engine_up->getPointerToFunction(&function);

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