[lldb] Enable std::pair in CxxModuleHandler

[teemperor]

Summary

This adds support for substituting std::pair instantiations with enabled import-std-module.

With the fixes in parent revisions we can currently substitute a single pair (however, a result that
returns a second pair currently causes LLDB to crash while importing the second template
instantiation).

[aprantl]

lldb/test/API/commands/expression/import-std-module/pair/TestPairFromStdModule.py

10

Does this cause any issues if the class name here is not unique?

[shafik]

Do we understand how to fix the crash in the case where we get a pair back? I am not sure how frequent the use case is.

[teemperor]

In D85141#2191229, @shafik wrote:

Do we understand how to fix the crash in the case where we get a pair back? I am not sure how frequent the use case is.

Haven't looked at that yet, but that's the next step :)

lldb/test/API/commands/expression/import-std-module/pair/TestPairFromStdModule.py

10

https://reviews.llvm.org/D83767 is actually there to address this (FWIW, we already have several 'TestCase' class names, so this isn't changing the situation regarding this).

lldb/source/Plugins/ExpressionParser/Clang/CxxModuleHandler.cpp

std::initializer_list<const char *> supported_names = {
       "stack",
       "vector",
       // pointers
       "shared_ptr",
       "unique_ptr",
       "weak_ptr",
       // utility
       "allocator",
+      "pair",
   };
   m_supported_templates.insert(supported_names.begin(), supported_names.end());
 }
 
 /// Builds a list of scopes that point into the given context.
 ///
 /// \param sema The sema that will be using the scopes.
 /// \param ctxt The context that the scope should look into.

lldb/test/API/commands/expression/import-std-module/pair/Makefile

+USE_LIBCPP := 1
+CXX_SOURCES := main.cpp
+include Makefile.rules

lldb/test/API/commands/expression/import-std-module/pair/TestPairFromStdModule.py

+"""
+Test basic std::pair functionality.
+"""
+
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class TestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @add_test_categories(["libc++"])
+    @skipIf(compiler=no_match("clang"))
+    def test(self):
+        self.build()
+
+        lldbutil.run_to_source_breakpoint(self,
+            "// Set break point at this line.", lldb.SBFileSpec("main.cpp"))
+
+        self.runCmd("settings set target.import-std-module true")
+
+        self.expect_expr("pair_int.first", result_type="int", result_value="1234")
+        self.expect_expr("pair_int.second", result_type="int", result_value="5678")
+        self.expect("expr pair_int", substrs=['first = 1234, second = 5678'])
 No newline at end of file

lldb/test/API/commands/expression/import-std-module/pair/main.cpp

+#include <utility>
+
+int main(int argc, char **argv) {
+  std::pair<int, int> pair_int(1234, 5678);
+  return 0; // Set break point at this line.
+}