using GDB with C-Preprocessor directives (Macros)

[Puneet Singhal]

Title: using GDB with C-Preprocessor directives (Macros)



Hi Aditya
 
for debugging Macros, u cannot use GDB bcoz GDB uses 
code after preprocessing.
 
if you r using gcc then u can use the -E switch to only 
pre process and not compile or link.
trap the output in a file and check out the expansion 
of the macros.
 
have fun,
Puneet

  this for quite some time and would sincerely 
  appreciate any help. 
  I am trying to use gdb for a C program which makes 
  heavy use of C macros. 
  The function ldpCreateIncarn() is called with 
  parameter u2IncarnId set to 0. 
  UINT1 ldpCreateIncarn (UINT2 u2IncarnId) 
  {    
  UINT1 u1HoldPrio; 
     LDP_ASSERT(u2IncarnId == 
  LDP_CUR_INCARN);    if ( 
  LDP_INCARN_STATUS(u2IncarnId) == ACTIVE )     {        return LDP_FAILURE; 
     } 
     gblTmrMemChkId = 1;    gblSNMPMemChkId = 1; . . . } 
  After call to LDP_INCARN_STATUS(u2IncarnId) the 
  value of u2IncarnId MYSTERIOUSLY changes to 
  1.LDP_INCARN_STATUS is a macro defined as follows 
  #define LDP_INCARN_STATUS(x) 
  (gLdpInfo.LdpIncarn[(x)].IncarnRowStatus) 
  ...it only reads the status from a global 
  data-stucture and checks to see if it is ACTIVE. It does not change the value 
  of "x" in any way.
  But after processing this macro the value of 
  u2IncarnId changes unexplicably ???? 
  Also in this function I have some other Macros 
  like 
  INIT_LBL_MGR_INFO(u2IncarnId) which are defined as #define INIT_LBL_MGR_INFO(x) 
  gLdpInfo.LdpIncarn[(x)].LdpLblMgrInfo.u4NumGrpsActive = LDP_ZERO; 
  At the time of entering such macros u2IncarnId is 
  set to 0 but after processing the macro its value cahnges to 168 !! 

  (gdb) p u2IncarnId $19 = 0 (gdb) n (gdb) p u2IncarnId $20 = 
  168 
  If I am missing something obvious please forgive 
  me. I have spent the whole day trying to figure out where I am going wrong. Thanks 
  in Advance, Aditya