fix(libc): list stack return address candidates in Windows backtrace reports

core/libs/prx/libc/CMakeLists.txt

@@ -569,5 +569,11 @@ if(MINGW)
         set_target_properties(windows_exception_tests PROPERTIES EXCLUDE_FROM_ALL FALSE)
         add_test(NAME windows_exceptions COMMAND windows_exception_tests)
         set_tests_properties(windows_exceptions PROPERTIES ENVIRONMENT_MODIFICATION "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>")
+        add_test_executable(windows_backtrace_report_tests ${LIBS_INCLUDE_DIR}/tests/WindowsBacktraceReport.cpp)
+        target_link_libraries(windows_backtrace_report_tests PRIVATE libc)
+        add_test(NAME windows_backtrace_report COMMAND windows_backtrace_report_tests)
+        set_tests_properties(windows_backtrace_report PROPERTIES TIMEOUT 20
+            ENVIRONMENT_MODIFICATION "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>"
+            PASS_REGULAR_EXPRESSION "aborting[^~]*SIGABRT. on thread[^~]*stack return address candidates:[^~]*rsp[+]0x")
     endif()
 endif()

core/libs/prx/libc/src/specifics/windows/CrashReport.cpp

@@ -31,6 +31,7 @@ void Report(const char* format, ...) {
 }
 
 void ReportAllThreads();
+void ReportStackCandidates(std::uint64_t rsp, int limit, std::uint64_t span);
 
 void DescribeAddress(std::uint64_t address, char* buffer, std::size_t size) {
     HMODULE module = nullptr;
@@ -296,16 +297,7 @@ LONG WINAPI ReportCrash(EXCEPTION_POINTERS* info) {
         if (next <= frame) break;
         frame = next;
     }
-    Report("  stack return address candidates:\n");
-    int printed = 0;
-    for (std::uint64_t slot = context->Rsp; printed < 16 && slot < context->Rsp + 0x2000; slot += 8) {
-        if (!IsReadable(slot)) break;
-        const auto value = *reinterpret_cast<const std::uint64_t*>(slot);
-        if (!IsExecutable(value)) continue;
-        DescribeAddress(value, line, sizeof(line));
-        Report("    [rsp+0x%llx] %s\n", static_cast<unsigned long long>(slot - context->Rsp), line);
-        ++printed;
-    }
+    ReportStackCandidates(context->Rsp, 16, 0x2000);
     if (context->Rip == 0 || !IsExecutable(context->Rip)) {
         // A jump into nothing usually follows a return through a clobbered frame; the frames that just
         // returned are still below rsp.
@@ -433,6 +425,20 @@ DWORD WINAPI HangWatchdog(LPVOID param) {
     return 0;
 }
 
+void ReportStackCandidates(std::uint64_t rsp, int limit, std::uint64_t span) {
+    char line[256];
+    Report("  stack return address candidates:\n");
+    int printed = 0;
+    for (std::uint64_t slot = rsp; printed < limit && slot < rsp + span; slot += 8) {
+        if (!IsReadable(slot)) break;
+        const auto value = *reinterpret_cast<const std::uint64_t*>(slot);
+        if (!IsExecutable(value)) continue;
+        DescribeAddress(value, line, sizeof(line));
+        Report("    [rsp+0x%llx] %s\n", static_cast<unsigned long long>(slot - rsp), line);
+        ++printed;
+    }
+}
+
 // abort() and the UCRT's invalid-parameter path end the process with a silent fast fail
 // (0xc0000409); both are reported with the calling thread's stack first.
 void ReportBacktrace(const char* what, bool reportThreads) {
@@ -444,6 +450,7 @@ void ReportBacktrace(const char* what, bool reportThreads) {
         DescribeAddress(reinterpret_cast<std::uint64_t>(frames[i]), line, sizeof(line));
         Report("    #%u %s\n", static_cast<unsigned>(i), line);
     }
+    ReportStackCandidates(reinterpret_cast<std::uint64_t>(__builtin_frame_address(0)), 32, 0x4000);
     if (reportThreads) ReportAllThreads();
     std::fflush(stderr);
 }

core/libs/tests/WindowsBacktraceReport.cpp

@@ -0,0 +1,12 @@
+#include <cstdio>
+#include <cstdlib>
+#include "../prx/libc/include/general/VabiMacros.hpp"
+
+extern "C" int* APS5_VABI __error_nid_postfix();
+
+int main() {
+    if (__error_nid_postfix() == nullptr) return 1;
+    _set_abort_behavior(0, _WRITE_ABORT_MSG | _CALL_REPORTFAULT);
+    std::fputs("aborting\n", stderr);
+    std::abort();
+}