Strange bug in egcs-1.1.2 suspected

[Jeffrey A Law]

  In message < 37665FF4.F7203D26@darmstadt.gmd.de >you write:
  > -------------------------------------------------------------
  > #include <stdio.h>
  > 
  > int
  > main(int argc, char **argv)
  > {
  >     struct {char c1, c2, c3, c4;} t;
  >     t.c4 = 0x78; t.c3 = 0x56; t.c2 = 0x34; t.c1 = 0x12;
  >     printf("0x%x\n", *((unsigned long*) &t));
  >     return 0;
  > }
  > -------------------------------------------------------------
  > Remember, the following is compiled with egcs-1.1.2 where Mark's
  > aliasing framework is disabled by default:
  > 
  > pommnitz ~/alias>gcc aliasorig.c -o aliasorig
  > pommnitz ~/alias>./aliasorig 
  > 0x78563412
  > pommnitz ~/alias>gcc -O2 aliasorig.c -o aliasorig
  > pommnitz ~/alias>./aliasorig 
  > 0x12
  > pommnitz ~/alias>gcc -O2 -fno-strict-aliasing aliasorig.c -o aliasorig
  > pommnitz ~/alias>./aliasorig 
  > 0x12
This is a known bug in egcs-1.1.2 -- it is not related to strict aliasing.
Though the code is not valid according to the aliasing rules of ISO/ANSI.


  > #include <stdio.h>
  > 
  > #define noalias(type, ptr) (((union { type __x__; __typeof__(*(ptr)) __y__;
  > } *)(ptr))->__x__)
  > 
  > int
  > main(int argc, char **argv)
  > {
  >     struct {char c1, c2, c3, c4;} t;
  >     t.c4 = 0x78; t.c3 = 0x56; t.c2 = 0x34; t.c1 = 0x12;
  >     printf("0x%x\n", noalias (unsigned long, &t));
  >     return 0;
  > }
  > -------------------------------------------------------------
  > 
  > The result:
  > pommnitz ~/alias>gcc -O2 alias2.c -o alias2
  > pommnitz ~/alias>./alias2
  > 0x12
  > 
  > Still not what we want. OK, next try:
No surprise since the bug in egcs-1.1.2 isn't related to type based aliasing.

  > Can somebody comment on this?
Yea, there was a code gen bug in egcs-1.1.2 independent of strict aliasing
that caused this code to blow up.  That bug has been fixed.  All three
versions produce the correct answers with gcc-2.95, even though correctness
for the first one can not be guaranteed due to strict aliasing violations.

jeff