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[lldb][windows] add support for out of PATH python.dll resolution #162509

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merged 4 commits into from
Oct 9, 2025
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[lldb][windows] add support for out of PATH python.dll resolution #162509

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37cf46e
[lldb][windows] add support for out of PATH python.dll resolution
charles-zablit Oct 8, 2025
2f7a6f1
fixup! [lldb][windows] add support for out of PATH python.dll resolution
charles-zablit Oct 8, 2025
e9625a4
address comments
charles-zablit Oct 9, 2025
93c0a4b
fixup! address comments
charles-zablit Oct 9, 2025
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6 changes: 6 additions & 0 deletions lldb/cmake/modules/AddLLDB.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,12 @@ function(add_lldb_executable name)
)

target_link_libraries(${name} PRIVATE ${ARG_LINK_LIBS})
if(WIN32)
list(FIND ARG_LINK_LIBS liblldb LIBLLDB_INDEX)
if(NOT LIBLLDB_INDEX EQUAL -1)
target_link_options(${name} PRIVATE "/DELAYLOAD:$<TARGET_FILE_BASE_NAME:liblldb>.dll")
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Any particular reason for using $<TARGET_FILE_BASE_NAME:liblldb>.dll rather than the more straightforward $<TARGET_FILE_NAME:liblldb>?

This patch broke compilation for mingw targets, as these options are specific to the MSVC style build case - and for that case, the DLL name we'd like to pass here has a lib prefix, i.e. liblldb.dll, not lldb.dll. So instead of trying to manually reapply a prefix and add .dll at the end, it seems more straightforward to me to just use $<TARGET_FILE_NAME:liblldb> which should give the right string in both cases?

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This used to be gated behind a if(MSVC) check in the downstream patch: swiftlang@af218c3. I think that with #162831 we will get a complete solution as if LLDB_PYTHON_DLL_RELATIVE_PATH is not set, the mechanism to add to the DLL search path will not even be compiled. If it's set, then it will only work for MSVC and mingw and there will be a warning if it's a different compiler.

which should give the right string in both cases?

I agree, this is much better 👍

endif()
endif()
if(CLANG_LINK_CLANG_DYLIB)
target_link_libraries(${name} PRIVATE clang-cpp)
else()
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4 changes: 4 additions & 0 deletions lldb/tools/driver/CMakeLists.txt
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Expand Up @@ -34,6 +34,10 @@ add_dependencies(lldb
${tablegen_deps}
)

if(DEFINED LLDB_PYTHON_DLL_RELATIVE_PATH)
target_compile_definitions(lldb PRIVATE LLDB_PYTHON_DLL_RELATIVE_PATH="${LLDB_PYTHON_DLL_RELATIVE_PATH}")
endif()

if(LLDB_BUILD_FRAMEWORK)
# In the build-tree, we know the exact path to the framework directory.
# The installed framework can be in different locations.
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52 changes: 52 additions & 0 deletions lldb/tools/driver/Driver.cpp
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Expand Up @@ -22,14 +22,21 @@
#include "lldb/Host/MainLoop.h"
#include "lldb/Host/MainLoopBase.h"
#include "lldb/Utility/Status.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/ConvertUTF.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/WithColor.h"
#include "llvm/Support/raw_ostream.h"

#ifdef _WIN32
#include "llvm/Support/Windows/WindowsSupport.h"
#endif

#include <algorithm>
#include <atomic>
#include <bitset>
Expand Down Expand Up @@ -426,6 +433,47 @@ SBError Driver::ProcessArgs(const opt::InputArgList &args, bool &exiting) {
return error;
}

#ifdef _WIN32
/// Returns the full path to the lldb.exe executable.
inline std::wstring GetPathToExecutableW() {
// Iterate until we reach the Windows API maximum path length (32,767).
std::vector<WCHAR> buffer;
buffer.resize(MAX_PATH /*=260*/);
while (buffer.size() < 32767) {
if (GetModuleFileNameW(NULL, buffer.data(), buffer.size()) < buffer.size())
return std::wstring(buffer.begin(), buffer.end());
buffer.resize(buffer.size() * 2);
}
return L"";
}

/// Resolve the full path of the directory defined by
/// LLDB_PYTHON_DLL_RELATIVE_PATH. If it exists, add it to the list of DLL
/// search directories.
void AddPythonDLLToSearchPath() {
std::wstring modulePath = GetPathToExecutableW();
if (modulePath.empty()) {
llvm::errs() << "error: unable to find python.dll." << '\n';
return;
}

SmallVector<char, MAX_PATH> utf8Path;
if (sys::windows::UTF16ToUTF8(modulePath.c_str(), modulePath.length(),
utf8Path))
return;
sys::path::remove_filename(utf8Path);
sys::path::append(utf8Path, LLDB_PYTHON_DLL_RELATIVE_PATH);
sys::fs::make_absolute(utf8Path);

SmallVector<wchar_t, 1> widePath;
if (sys::windows::widenPath(utf8Path.data(), widePath))
return;

if (sys::fs::exists(utf8Path))
SetDllDirectoryW(widePath.data());
}
#endif

std::string EscapeString(std::string arg) {
std::string::size_type pos = 0;
while ((pos = arg.find_first_of("\"\\", pos)) != std::string::npos) {
Expand Down Expand Up @@ -728,6 +776,10 @@ int main(int argc, char const *argv[]) {
"~/Library/Logs/DiagnosticReports/.\n");
#endif

#if defined(_WIN32) && defined(LLDB_PYTHON_DLL_RELATIVE_PATH)
AddPythonDLLToSearchPath();
#endif

// Parse arguments.
LLDBOptTable T;
unsigned MissingArgIndex;
Expand Down
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