[cfe-users] Null CFGBlock successors

[Derrick McKee via cfe-users]

Hi,

I am writing a ClangTool that visits every function in a module, and edits
source code based on the CFG.  For a function I want to instrument,
however, the CFG produces blocks that list a successor as NULL.  This is a
problem because I need to perform a breadth-first search of the CFG, and I
cannot because of the null successor.  I have listed the result of
cfg->dump() below.  What could be the cause of this?  Any help would be
appreciated.  Thanks.

 [B18 (ENTRY)]
   Succs (1): B17

 [B1]
   1: i += 30
   Preds (1): B2
   Succs (1): B5

 [B2]
   1: strlen(json)
   2: MarsSendBlocking(1, json, [B2.1])
   Preds (2): B3 B4
   Succs (1): B1

 [B3]
   Preds (1): B4
   Succs (1): B2

 [B4]
   T: if <null expr>
   Preds (1): B5
   Succs (2): B3 B2

 [B5]
   T: for (; ; ...)
   Preds (2): B1 B6
   Succs (2): B4 NULL

 [B6]
   1: strlen(json)
   2: MarsSendBlocking(1, json, [B6.1])
   Succs (1): B5

 [B7]
   1: i++
   Preds (2): B8 B9
   Succs (1): B10

 [B8]
   Preds (1): B9
   Succs (1): B7

 [B9]
   1: char tempString[6];
   T: if <null expr>
   Preds (1): B10
   Succs (2): B8 B7

 [B10]
   T: for (...; ; ...)
   Preds (2): B7 B11
   Succs (2): B9 NULL

 [B11]
   1: ndc_str[14] = 0
   2: npi_str[12] = 0
   3: zip_str[5] = 0
   4: t.tm_isdst = -1
   5: mktime(&t)
   6: time_prescribed = [B11.5]
   7: printf("year:%u month:%u day:%u hour:%u min:%u sec:%u\n", t.tm_year,
t.tm_mon, t.tm_mday, t.tm_hour, t.tm_min, t.tm_sec)
   8: i = 0
   Preds (1): B12
   Succs (1): B10

 [B12]
   T: if <null expr>
   Preds (2): B13 B14
   Succs (2): B11 B0

 [B13]
   Preds (1): B14
   Succs (1): B12

 [B14]
   T: if <null expr>
   Succs (2): B13 B12

 [B15]
   1: i++
   Preds (1): B16
   Succs (1): B16

 [B16]
   T: for (...; ; ...)
   Preds (2): B15 B17
   Succs (2): B15 NULL

 [B17]
   1: char ndc_str[15];
   2: char npi_str[13];
   3: char zip_str[6];
   4: char dosageIntervals;
   5: int last_msg_idx;
   6: int i;
   7: struct tm t;
   8: time_t time_prescribed;
   9: i = 0
   Preds (1): B18
   Succs (1): B16

 [B0 (EXIT)]
   Preds (1): B12

-- 
Derrick McKee
Ph.D. Student Computer Science
Purdue University
SensorHound, Inc.
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