[PATCH] vcruntime140_1: Use return address from catch block routine if not provided by catch block info.

[Daniel Lehman]

Signed-off-by: Daniel Lehman <dlehman25 at gmail.com>

---
this sample runs an infinite loop of 'catch: int' built with vs2019:
cl /MD /EHs simple.cpp
void test_crash_simple(void)
{
    try
    {
        throw 0x42;
    }
    catch (int x)
    {
        printf("catch: int\n");
    }
}

ret_addr isn't set - remains zero - and the return address in the catch record
is the start of the function (ExceptionInformation[8] = ci.ret_addr + BeginAddress)

call_catch_block4 sees this non-null address and resumes at the start of the function
where the exception happened and hits the exception again, leading to a crash

this change only sets the return address if non-zero.  the catch record is already
zeroed by the memset.  call_catch_block4 already defaults to the address returned
from the handler and only uses the one from the catch_record if non-null

---
 dlls/vcruntime140_1/except_x86_64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/dlls/vcruntime140_1/except_x86_64.c b/dlls/vcruntime140_1/except_x86_64.c
index 4cc6897223..e1a39c0662 100644
--- a/dlls/vcruntime140_1/except_x86_64.c
+++ b/dlls/vcruntime140_1/except_x86_64.c
@@ -603,7 +603,8 @@ static inline void find_catch_block4(EXCEPTION_RECORD *rec, CONTEXT *context,
                 (ULONG_PTR)rva_to_ptr(ci.handler, dispatch->ImageBase);
             catch_record.ExceptionInformation[6] = (ULONG_PTR)untrans_rec;
             catch_record.ExceptionInformation[7] = (ULONG_PTR)context;
-            catch_record.ExceptionInformation[8] = (ULONG_PTR)rva_to_ptr(
+            if (ci.ret_addr)
+                catch_record.ExceptionInformation[8] = (ULONG_PTR)rva_to_ptr(
                     ci.ret_addr + dispatch->FunctionEntry->BeginAddress, dispatch->ImageBase);
             RtlUnwindEx((void*)frame, (void*)dispatch->ControlPc, &catch_record, NULL, &ctx, NULL);
         }
-- 
2.17.1