sdcc/support/regression/tests/bug2729218.c

   1 /** bug2729218.c
   2 */
   3
   4 #include <testfwk.h>
   5
   6 /*
   7
   8 sdcc appears to compile the following file incorrectly.  I have attached
   9 the C source code, and the generated assembly code, with some comments
  10 that explain the bug.
  11
  12 The basic problem is that a memory location is post-incremented, but
  13 the register variable that shadows that memory location is NOT
  14 increment, and this incorrect value is used in later calculations.
  15
  16 I compiled it with these options:
  17
  18     sdcc -mmcs51 --model-small --std-sdcc99 --code-loc 0xf000 -c bug.c
  19
  20 Here is the "sdcc -v" output:
  21
  22     SDCC : mcs51/gbz80/z80/avr/ds390/pic16/pic14/TININative/xa51/ds400/hc08 2.9.1 #5422 (Apr  3 2009) (UNIX)
  23
  24 */
  25
  26 struct iglobals
  27 {
  28   unsigned char rx_byte;
  29   unsigned char input_cnt;
  30 };
  31
  32 #if !defined(__SDCC_sm83) && !defined(__SDCC_pdk14) && !defined(__SDCC_f8)
  33 #define ig (*(__idata struct iglobals *) 0xf0)
  34 #else
  35 struct iglobals ig;
  36 #endif
  37
  38 unsigned char count;
  39
  40 unsigned char
  41 do_command(void)
  42 {
  43   // In the following statement, the post-increment is saved in
  44   // memory, but not in the value stored in the r7 register
  45   count = ig.input_cnt++;
  46
  47   // In the following statement, the value of "input_cnt" stored in
  48   // the r7 register is used, but it is wrong (never incremented).
  49   return ig.input_cnt;
  50 }
  51
  52 void testBug(void)
  53 {
  54 #ifdef __SDCC
  55         ig.rx_byte = 0;
  56         ig.input_cnt = 1;
  57
  58         ASSERT (do_command() == 2);
  59         ASSERT (ig.input_cnt == 2);
  60         ASSERT (count == 1);
  61 #endif
  62 }