[Bug 725] New: busybox awk will wrongly cast integer to string causing functions to fail.

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=725

           Summary: busybox awk will wrongly cast integer to string causing
                    functions to fail.
           Product: Busybox
           Version: 1.12.x
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
        AssignedTo: unassigned at busybox.net
        ReportedBy: bugzilla at lordy.org.uk
                CC: busybox-cvs at busybox.net
   Estimated Hours: 0.0


The busybox awk will infer a variable type from its RHS usage rather than the
expression used to create it. Gawk does not have this problem. It sounds
trivial, and arguably awk implementation dependent, but the following example
shows the full extent of the problem:

In the code below function a() returns 0, b() returns a() and c() returns b().
The a
Code (shell script)=====
awk '
function a() {
  return 0;
}

function b(tmp) {
        tmp= a();
        print "DBG:result="tmp;  #This line forces incorrect cast of tmpc to
string
        return tmp;
}
function c(tmpc) {
        tmpc= b();
        return tmpc;
}

BEGIN {
  print "a():"(a()?"true":"false");
  print "b():"(b()?"true":"false");
  print "c():"(c()?"true":"false");
}
'
==============
Run test: echo | sh ./file.sh
==============
Expected output (as with gawk):
===============
# echo | /tmp/q.sh
a():false
DBG:result=0
b():false
DBG:result=0
c():false
================
Actual output : c() returns the string "0" rather than the number 0.
================
# echo | /tmp/q.sh
a():false
DBG:result=0
b():false
DBG:result=0
c():true
================
As noted in the code, it is the debug line that triggers the string cast.
This may may a lot of awk scripts behave (more) oddly than they would normally.

Workaround: Do not use boolean decision statements without operations, as the
0 may be case to a "0" at any point. 

eg. replace if(c()) with if(c()!=0) or (if(c()+0)), 

similarly, while() , (?:) etc.
=================
My speculation:
It looks like the interpreter, when in function c() is going to b() to
determine its return type (integer or string), however it is using the 
debug print statement, rather than going to a().


Observed with busybox 1.12.3 on Linux 2.4.20 (Tomato WRT54G)
busybox 1.12.4 on Linux 2.6.15-sigma (NMT HDX 1000)


-- 
Configure bugmail: https://bugs.busybox.net/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.