Microsoft KB Archive/85306

= FIX: Incorrect Results from Mixed-Type Expressions =

Article ID: 85306

Article Last Modified on 12/1/2003

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APPLIES TO


 * Microsoft FORTRAN Compiler 4.0
 * Microsoft FORTRAN Compiler 4.01
 * Microsoft FORTRAN Compiler 4.1
 * Microsoft FORTRAN Compiler 5.0
 * Microsoft FORTRAN Compiler 5.1
 * Microsoft FORTRAN Compiler 4.1
 * Microsoft FORTRAN Compiler 5.0
 * Microsoft FORTRAN Compiler 5.1

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This article was previously published under Q85306



SYMPTOMS
A program compiled with Microsoft FORTRAN version 4.0, 4.01, 4.1, 5.0, or 5.1 under MS-DOS or version 4.1, 5.0, or 5.1 under OS/2 can generate incorrect results on mixed-type expressions when an INTEGER variable is used on both sides of an equation. The /Od compiler option, which is used to suppress optimization, has no effect.



CAUSE
The compiler is incorrectly converting intermediate values to the INTEGER type used on both sides of the arithmetic statement.



RESOLUTION
To avoid this problem, keep data types consistent within arithmetic expressions by using the intrinsic functions to force the conversion of intermediate expressions to the proper data type.



STATUS
Microsoft has confirmed this to be a problem in Microsoft FORTRAN versions 4.0, 4.01, 4.1, 5.0, and 5.1 for MS-DOS and versions 4.1, 5.0, and 5.1 for OS/2. This problem was corrected in FORTRAN PowerStation.



Sample Code 1
The following code reproduces the problem: integer*4 i, j     i=10 j=i-1.1  ! correct (10.0 - 1.1 = 8.9, truncated to 8) i=i-1.1  ! incorrect  (10 - 1 = 9)

write(*,*) 'j=',j,' i=',i     ! outputs j=8 i=9 end

Sample Code 2
The following code illustrates the solution: integer*4 i, j     i=10 j=i-1.1        ! correct (10.0 - 1.1 = 8.9, truncated to 8)

i=real(i)-1.1  ! convert i to real, then set to an integer ! variable when assigned write(*,*) 'j=',j,' i=',i     ! correct output generated end

Additional query words: 4.00 5.10 5.00

Keywords: kbfix KB85306

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