Conference turris::decladebug

883.0. "Function arg type changes after I step into the function." by GALVIA::STONES (Tom Stones) Thu Mar 13 1997 05:13

I'm debugging a C++ code which includes the bits of source shown below.  One of the
overloaded member functions called    RCS_T::GetEmptyBufForSend   
has an argument of type imc_block_t.   I build a shared library including these
functions and call them from a main module that declares variables of type imc_block_t 
and passes them as arguments to   RCS_T::GetEmptyBufForSend.

The problem is that ladebug shows the argument type properly before I enter the
function, but shows the wrong arg type when inside the function.  The type imc_lkinfo
appears in the header file that declares type imc_block_t, but is not used at all in my
code (although it is used in libimc.a which is linked into my library). 

Here's what ladebug did:
...
(ladebug) 
stopped at [void Sender(void):65 0x120002f58]
     65   status = rcs1->GetEmptyBufForSend(sndWakeH, sndEP, &b1, &index1);
(ladebug) whatis sndWakeH
unsigned long sndWakeH
(ladebug) whatis RCS_t::GetEmptyBufForSend
int RCS_t::GetEmptyBufForSend(imc_block_t, MCMEPADDR&, BufId_t*, int*)
(ladebug) s                   
stopped at [int RCS_t::GetEmptyBufForSend(imc_lkinfo, MCMEPADDR&, BufId_t*, int*):351
0x3ffbffe83c0]
    351     lock.ClusterLock(&(txRCS->lock));
(ladebug) whatis RCS_t::GetEmptyBufForSend
int RCS_t::GetEmptyBufForSend(imc_lkinfo, MCMEPADDR&, BufId_t*, int*)
(ladebug) t
>0  0x3ffbffe83c0 in ((RCS_t*)0x10000)->GetEmptyBufForSend(senderWakeHandle=<opaque>
bits = , sendAdr={ ... }, bufId=0x11ffff960, index=0x11ffff940) ./rcs.cxx:351
#1  0x120002f70 in Sender() rcstest.cxx:65
#2  0x1200030ec in main(argc=1, argv=0x11ffff9e8) rcstest.cxx:84
(ladebug) p senderWakeHandle
<opaque> bits = 
(ladebug) 


Here are extracts form the source:
imc.h:
  ...
  extern "C" {
  ...
  typedef long imc_key_t;
  typedef long imc_size_t;   
  typedef int  imc_perm_t;
  typedef int  imc_dir_t;
  typedef struct imc_lkinfo *imc_lkid_t;         <<<--- Not used.
  typedef int imc_asid_t;
  typedef int imc_mcid_t;
  typedef struct {
    int  num;
    char name[IMC_MAXHOSTS][MAXHOSTNAMELEN];
  } imc_hostinfo;
  typedef unsigned long imc_block_t;              <<<--- Used
  ...

rcs.h:
  ...
  #include imc.h
  ...
  class RCS_t {
  ...
  public:
  ...
  int GetEmptyBufForSend(MCMEPADDR &sendAdr, BufId_t *bufId, int *index);
  int GetEmptyBufForSend(imc_block_t senderWakeHandle, 
			 MCMEPADDR &sendAdr, BufId_t *bufId, int *index);
  ...


rcs.cxx:
  ...
  #include "rcs.h"
  #include "imc.h"
  ...
  inline int RCS_t::GetEmptyBufForSend(MCMEPADDR &sendAdr, 
				    BufId_t *bufId, int *index) {
  ...
  int RCS_t::GetEmptyBufForSend(imc_block_t senderWakeHandle,
			     MCMEPADDR &sendAdr, BufId_t *bufId, int *index) {
  ...


main.cxx
  ...
  #include "rcs.h"
  ...
  void Sender() {
    imc_block_t sndWakeH;
    RCS_t *rcs1 = new(&rcvRcsDesc) RCS_t;
    ...
    status = rcs1->GetEmptyBufForSend(sndWakeH, sndEP, &b1, &index1);

Thanks for the report.  I've added it to the C++ bugs list.

-Steve