test: py: LD_PRELOAD the C++ standard library when using ASan

When the ASan runtime is linked using --as-needed, its dependency on the
C++ standard library is stripped. This results to a failure to properly
handled exceptions when a C++ dynamically loaded .so is used, as in the
Python unit tests that load the libcamera Python module:

AddressSanitizer: CHECK failed: asan_interceptors.cpp:335 "((__interception::real___cxa_throw)) != (0)" (0x0, 0x0) (tid=32679)
    #0 0x7fa2f32e6c19 in CheckUnwind /var/tmp/portage/sys-devel/gcc-13.3.1_p20241025/work/gcc-13-20241025/libsanitizer/asan/asan_rtl.cpp:69
    #1 0x7fa2f330c9fd in __sanitizer::CheckFailed(char const*, int, char const*, unsigned long long, unsigned long long) /var/tmp/portage/sys-devel/gcc-13.3.1_p20241025/work/gcc-13-20241025/libsanitizer/sanitizer_common/sanitizer_termination.cpp:86
    #2 0x7fa2f3247824 in __interceptor___cxa_throw /var/tmp/portage/sys-devel/gcc-13.3.1_p20241025/work/gcc-13-20241025/libsanitizer/asan/asan_interceptors.cpp:335
    #3 0x7fa2f3247824 in __interceptor___cxa_throw /var/tmp/portage/sys-devel/gcc-13.3.1_p20241025/work/gcc-13-20241025/libsanitizer/asan/asan_interceptors.cpp:334
    #4 0x7fa2efb6da8b in operator() ../../src/py/libcamera/py_main.cpp:157
[...]

The issue has been reported in [1] and so far remains unfixed. Work
around it by preloading the C++ standard library.

[1] https://github.com/google/sanitizers/issues/934

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

meson.build

@@ -112,6 +112,8 @@ common_arguments = [
 c_arguments = []
 cpp_arguments = []
 
+cxx_stdlib = 'libstdc++'
+
 if cc.get_id() == 'clang'
     if cc.version().version_compare('<9')
         error('clang version is too old, libcamera requires 9.0 or newer')
@@ -137,6 +139,7 @@ if cc.get_id() == 'clang'
         cpp_arguments += [
             '-stdlib=libc++',
         ]
+        cxx_stdlib = 'libc++'
     endif
 
     cpp_arguments += [

test/py/meson.build

@@ -24,6 +24,12 @@ py_env.append('PYTHONPATH', pypathdir)
 if asan_enabled
     py_env.append('LD_PRELOAD', asan_runtime)
 
+    # Preload the C++ standard library to work around a bug in ASan when
+    # dynamically loading C++ .so modules.
+    stdlib = run_command(cxx, '-print-file-name=' + cxx_stdlib + '.so',
+                         check : true).stdout().strip()
+    py_env.append('LD_PRELOAD', stdlib)
+
     # Disable leak detection as the Python interpreter is full of leaks.
     py_env.append('ASAN_OPTIONS', 'detect_leaks=0')
 endif