[PATCH v2 2/2] test: unit test for longjmp

Heinrich Schuchardt xypron.glpk at gmx.de
Wed Mar 24 12:16:48 CET 2021

On 24.03.21 10:18, Andreas Schwab wrote:
> On Mär 22 2021, Sean Anderson wrote:
>> int test_longjmp_ret(int i)
>> {
>>      jmp_buf env;
>>      int ret;
>>      int foo = i;
>>      ret = setjmp(env);
>>      if (ret)
>>          return foo;
>>      foo = 0x1000;
>>      longjmp(env, i);
>>      /* We should not arrive here */
>>      return foo;
> This is undefined.  When modifying a non-volatile auto variable between
> setjmp and longjmp, there is no requirement that the value is preserved.
> Andreas.

Hello Andreas,

thank you for reviewing.

Your comment relates to the following paragraph in the C99 specification:

"All  accessible  objects  have  values,  and  all  other  components
of the  abstract  machine have  state,  as  of  the  time  the longjmp
function  was  called,  except  that  the  values  of objects  of
automatic  storage  duration  that  are  local  to  the  function
containing  the invocation  of  the  corresponding setjmp macro  that
do  not  have  volatile-qualified  type and  have  been  changed
between the setjmp invocation and longjmp call are indeterminate."

And foo is obviously "changed  between the setjmp invocation and longjmp

The current version of the patch is:

So I guess we have to declare env as volatile in setjmp() in this
version of the patch because it is changed between the setjmp and
longjmp invocations?

Best regards


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