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[clangd] Fix off-by-one error in CommandMangler #156593

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[clangd] Fix off-by-one error in CommandMangler #156593

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3 changes: 2 additions & 1 deletion clang-tools-extra/clangd/CompileCommands.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -270,7 +270,8 @@ void CommandMangler::operator()(tooling::CompileCommand &Command,
if (auto *DashDash =
ArgList.getLastArgNoClaim(driver::options::OPT__DASH_DASH)) {
auto DashDashIndex = DashDash->getIndex() + 1; // +1 accounts for Cmd[0]
for (unsigned I = DashDashIndex; I < Cmd.size(); ++I)
// Another +1 so we don't treat the `--` itself as an input.
for (unsigned I = DashDashIndex + 1; I < Cmd.size(); ++I)
SawInput(Cmd[I]);
Cmd.resize(DashDashIndex);
}
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10 changes: 10 additions & 0 deletions clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp
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Expand Up @@ -526,6 +526,16 @@ TEST(CommandMangler, RespectsOriginalSysroot) {
Not(HasSubstr(testPath("fake/sysroot"))));
}
}

TEST(CommandMangler, StdLatestFlag) {
const auto Mangler = CommandMangler::forTests();
tooling::CompileCommand Cmd;
Cmd.CommandLine = {"clang-cl", "-std:c++latest", "--", "/Users/foo.cc"};
Mangler(Cmd, "/Users/foo.cc");
// Check that the -std:c++latest flag is not dropped
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@HighCommander4 HighCommander4 Sep 3, 2025

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Not sure if this is the best test case for this change. -std:c++latest being dropped in transferCompileCommand() is a separate bug that will hopefully be fixed in the near future.

But I'm not sure how to write a more direct test for "transferCompileCommand() was not called", and the scenario being tested here is a valid one from a user expectation point of view.

EXPECT_THAT(llvm::join(Cmd.CommandLine, " "), HasSubstr("-std:c++latest"));
}

} // namespace
} // namespace clangd
} // namespace clang
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