MSVC /fsanitize-address-use-after-return: stack-buffer-underflow in makeTestInvoker during static test registration

Describe the bug When Catch2 and a test executable are both compiled with MSVC AddressSanitizer plus the experimental /fsanitize-address-use-after-return flag, the test binary aborts during static test registration (before main()), with ASan reporting a stack-buffer-underflow in the Catch::Detail::unique_ptr move constructor. The identical build with /fsanitize=address alone (no use-after-return) runs correctly. A clear and concise description of what the bug is.

Expected behavior No warnings. Catch interacts with AddressSanitizer correctly.

Reproduction steps repro.cpp: #include <catch_amalgamated.hpp> TEST_CASE("minimal", "[repro]") { REQUIRE(1 + 1 == 2); }

Build (Catch2 v3.15.3, amalgamated) + repro, all with the flag, then run: cl /EHsc -std:c++latest /MDd /Od /utf-8 /fsanitize=address /fno-sanitize-address-vcasan-lib /fsanitize-address-use-after-return /I extras /c extras/catch_amalgamated.cpp cl /EHsc -std:c++latest /MDd /Od /utf-8 /fsanitize=address /fno-sanitize-address-vcasan-lib /fsanitize-address-use-after-return /I extras repro.cpp catch_amalgamated.obj .\repro.exe --list-tests

Result (with the flag): ==16880==ERROR: AddressSanitizer: stack-buffer-underflow WRITE of size 8 thread T0 #0 Catch::Detail::unique_ptr::unique_ptr catch_amalgamated.hpp:949 #1 Catch::Detail::make_unique<TestInvokerAsFunction, void(&)(void)> catch_amalgamated.hpp:1029 #2 Catch::makeTestInvoker(void()()) catch_amalgamated.cpp:7700 #3 dynamic initializer for 'autoRegistrar1' frame has 1 object: [32, 40) 'compiler temporary' HINT: this may be a false positive if your program uses some custom stack unwind mechanism

Result (without /fsanitize-address-use-after-return) — lists and runs normally.

Platform information: OS: Windows 11 Compiler: MSVC 19.51 / VS 2026 (14.51.36231) Catch2: v3.15.3 (also reproduced on devel via the non-amalgamated catch_test_registry.cpp / catch_unique_ptr.hpp)

Additional context I can't tell if this is a problem in Catch2 or in AddressSanitizer. Filing here first, if you determine that catch is behaving correctly I'll move it to Microsofts ASan.