[vox-tech] Where setjmp/longjmp went after C

[Haiying Wu]

"[vox-tech] Where setjmp/longjmp went after C" is a
good article. But I have to point out a possible
mistake.

I think there are risks to define macro"#define 
JB_ENDTRY  }JB_ULN}".

for example, in code: 

void b( char volatile c )
{
  int caught=0;

  printf( "entered b with c=%c\n", c );
  JB_TRY( &caught ) {
    printf( "doing f\n" );
    f( c );
    printf( "did f\n" );
    g( c );
    printf( "did g\n" );
  } JB_CATCH( EXCEP_MATHERR ) {
    printf( "caught MATHERR exception in b\n" );
    JB_RAISE( EXCEP_INVALIDARGS );
  } JB_CATCHDEFAULT {
    printf( "caught some other exception... c=%c,
caught=%d\n", c, caught );
    JB_RAISE( caught );
  } JB_ENDTRY;
  printf( "leaving b\n" );
}

It's OK. But what if there is no another exception
raised in catch block or catch-default block? See the
following code:

  JB_CATCH( EXCEP_MATHERR ) {
   printf( "caught MATHERR exception in b\n" );
    /*JB_RAISE( EXCEP_INVALIDARGS );*/ //no new
exception raised
  }

then, JB_ENDTRY will be executed after JB_CATCH block
.
So, JB_ULN will be executed twice, it is dangerous!

A possible solution to this problem is to:
(1)#define JB_ENDTRY }}
(2)#define JB_NORMAL_TERMINATE JN_ULN
(3)add "JB_NORMAL_TERMINATE" at the end of normal code
(try block).
So the code becomes:
  JB_TRY( &caught ) {
   ...
  JB_NORMAL_TERMINATE;
  } JB_CATCH( EXCEP_MATHERR ) {
  ...
  } JB_CATCHDEFAULT {
  ...
  } JB_ENDTRY;

Certainly, to eliminate the explicit statement
"JB_NORMAL_TERMINATE" in user code, we can define
macro JB_FIRST_CATCH:
#define JB_FIRST_CATCH JB_ULN;JB_CATCH

By user's explict code or by complier's implicit
translate, the final code would look like:

  JB_TRY( &caught ) {
   ...
  } JB_FIRST_CATCH( EXCEP_MATHERR ) {
  ...
  } JB_CATCH( EXCEP_... ) {
  ...
  } JB_CATCH( EXCEP_... ) {
  ...
  } JB_CATCHDEFAULT {
  ...
  } JB_ENDTRY;


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