KB105932 - FIX: String Concatenation May Cause Memory Errors

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The following two sample programs demonstrate a memory loss due to string concatenation in the argument list. In both of the following examples, using a temporary variable for the concatenated strings avoids the memory leak.

Sample Code 1

C Compile options needed: none
      character*40 c1,c2
      c1 = 'abcd'
      c2 = 'efgh'
      k = 0
      do i=1,500000
        if(c1//c2 .eq. 'Never') k = k + 1
      end do
      end

The code above will run very slowly, and eventually generate:

run-time error F6700
- heap space limit exceeded

Sample Code 2

C Compile options needed: none
      character fmtout*20,label(1,3)*(9)
      double precision value
      data (label(1,j),j=1,3)/' Label',' Output',' Test'/ 
      data value/3.14159/ 
      fmtout='f10.3'
      write(6,'(3a,''='','//fmtout//')')(label(1,j),j=1,3),value
      end

The above code on execution will generate:

DOSXMSF : error DX2010: invalid pointer passed to free or realloc : 0005F0F8h.
DOSXMSF : error DX2010: invalid pointer passed to free or realloc : 0005F0F8h.
Label Output Test = 3.142

The code does run to completion because this type of DOS-extender error is not fatal.

FIX: String Concatenation May Cause Memory Errors

SYMPTOMS

RESOLUTION

STATUS

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Sample Code 1

Sample Code 2