[csmith-dev] Alignment of struct members cause target dependent checksum

[Kees Bakker]

Hi,

Csmith can generate tests with unions and struct where the result
is target dependent.

Here is a small example.

   struct S1 {
      const volatile uint8_t  f10;
      int32_t  f11;
   };

   union U4 {
      const uint32_t  f0;
      struct S1  f2;
   };
   static union U4 g_1126 = {4294967294UL};

One of the tests I created was writing in g_1126.f2.f11 and reading
from g_1126.f0 for the checksum.

However, the struct member offset of f11 is not defined. For example GCC (i386)
uses an offset 4, but other (compliant C99 compilers) may use offset 2 or even 1.
(And that is without specifying "pack".)

In this case the checksum created with GCC (assuming GCC is correct) is not
valid for all other compilers.

What options do I have to let Csmith avoid such a construct?

Kind regards,
Kees Bakker