vsk created this revision.
vsk added a reviewer: jingham.
Herald added a subscriber: emaste.
vsk requested review of this revision.
Herald added a project: LLDB.
In general, it seems like the debugger should allow programs to load & run with
libraries as far as possible, instead of defaulting to being super-picky about
unavailable symbols.
This is critical on macOS/Darwin, as libswiftCore.dylib may 1) export a version
symbol using @available markup and then 2) expect that other exported APIs are
only dynamically used once the version symbol is checked. We can't open a
version of the library built with a bleeding-edge SDK on an older OS without
RTLD_LAXY (or pervasive/expensive @available markup added to dyld APIs).
See: https://lists.llvm.org/pipermail/lldb-dev/2021-March/016796.html
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D98879
Files:
lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
Index: lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
===================================================================
--- lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
+++ lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
@@ -573,6 +573,21 @@
std::unique_ptr<UtilityFunction>
PlatformPOSIX::MakeLoadImageUtilityFunction(ExecutionContext &exe_ctx,
Status &error) {
+ // Use lazy binding so as to not make dlopen()'s success conditional on
+ // forcing every symbol in the library. This is critical on macOS/Darwin, as
+ // a library may 1) export a version symbol using @available markup and then
+ // 2) expect that other exported APIs are only dynamically used once the
+ // version symbol is checked. (Previously, LLDB used RTLD_NOW=2, which made
+ // it impossible to load such libraries (e.g. libswiftCore.dylib)).
+ //
+ // In general, the debugger should allow programs to load & run with
+ // libraries as far as they can, instead of defaulting to being super-picky
+ // about unavailable symbols.
+ //
+ // The value "1" appears to imply lazy binding (RTLD_LAZY) on both Darwin
+ // and other POSIX OSes.
+#define DLOPEN_OPTIONS "1"
+
// Remember to prepend this with the prefix from
// GetLibdlFunctionDeclarations. The returned values are all in
// __lldb_dlopen_result for consistency. The wrapper returns a void * but
@@ -595,7 +610,7 @@
{
// This is the case where the name is the full path:
if (!path_strings) {
- result_ptr->image_ptr = dlopen(name, 2);
+ result_ptr->image_ptr = dlopen(name, )" DLOPEN_OPTIONS R"();
if (result_ptr->image_ptr)
result_ptr->error_str = nullptr;
return nullptr;
@@ -609,7 +624,7 @@
buffer[path_len] = '/';
char *target_ptr = buffer+path_len+1;
memcpy((void *) target_ptr, (void *) name, name_len + 1);
- result_ptr->image_ptr = dlopen(buffer, 2);
+ result_ptr->image_ptr = dlopen(buffer, )" DLOPEN_OPTIONS R"();
if (result_ptr->image_ptr) {
result_ptr->error_str = nullptr;
break;
@@ -620,6 +635,7 @@
return nullptr;
}
)";
+#undef DLOPEN_OPTIONS
static const char *dlopen_wrapper_name = "__lldb_dlopen_wrapper";
Process *process = exe_ctx.GetProcessSP().get();
Index: lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
===================================================================
--- lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
+++ lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
@@ -573,6 +573,21 @@
std::unique_ptr<UtilityFunction>
PlatformPOSIX::MakeLoadImageUtilityFunction(ExecutionContext &exe_ctx,
Status &error) {
+ // Use lazy binding so as to not make dlopen()'s success conditional on
+ // forcing every symbol in the library. This is critical on macOS/Darwin, as
+ // a library may 1) export a version symbol using @available markup and then
+ // 2) expect that other exported APIs are only dynamically used once the
+ // version symbol is checked. (Previously, LLDB used RTLD_NOW=2, which made
+ // it impossible to load such libraries (e.g. libswiftCore.dylib)).
+ //
+ // In general, the debugger should allow programs to load & run with
+ // libraries as far as they can, instead of defaulting to being super-picky
+ // about unavailable symbols.
+ //
+ // The value "1" appears to imply lazy binding (RTLD_LAZY) on both Darwin
+ // and other POSIX OSes.
+#define DLOPEN_OPTIONS "1"
+
// Remember to prepend this with the prefix from
// GetLibdlFunctionDeclarations. The returned values are all in
// __lldb_dlopen_result for consistency. The wrapper returns a void * but
@@ -595,7 +610,7 @@
{
// This is the case where the name is the full path:
if (!path_strings) {
- result_ptr->image_ptr = dlopen(name, 2);
+ result_ptr->image_ptr = dlopen(name, )" DLOPEN_OPTIONS R"();
if (result_ptr->image_ptr)
result_ptr->error_str = nullptr;
return nullptr;
@@ -609,7 +624,7 @@
buffer[path_len] = '/';
char *target_ptr = buffer+path_len+1;
memcpy((void *) target_ptr, (void *) name, name_len + 1);
- result_ptr->image_ptr = dlopen(buffer, 2);
+ result_ptr->image_ptr = dlopen(buffer, )" DLOPEN_OPTIONS R"();
if (result_ptr->image_ptr) {
result_ptr->error_str = nullptr;
break;
@@ -620,6 +635,7 @@
return nullptr;
}
)";
+#undef DLOPEN_OPTIONS
static const char *dlopen_wrapper_name = "__lldb_dlopen_wrapper";
Process *process = exe_ctx.GetProcessSP().get();
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