Microsoft KB Archive/111502

= BUG: SUBSTR Index Past End of String Incorrectly Assembles =

Article ID: 111502

Article Last Modified on 10/14/2003

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APPLIES TO


 * Microsoft Macro Assembler 6.0 Standard Edition
 * Microsoft Macro Assembler 6.0a
 * Microsoft Macro Assembler 6.0b
 * Microsoft Macro Assembler 6.1 Standard Edition
 * Microsoft Macro Assembler 6.1a
 * Microsoft Macro Assembler 6.11 Standard Edition

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This article was previously published under Q111502



SYMPTOMS
MASM 6.x will incorrectly assemble the SUBSTR directive and not generate the expected error if the index value is 1 (one) greater than the length of the string. The expected error is:

A2091: index value past end of string



STATUS
Microsoft has confirmed this to be a problem in the Microsoft Macro Assembler (MASM) versions 6.x. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.



MORE INFORMATION
The sample code below illustrates this behavior as well as the correct use of SUBSTR.

The SUBSTR directive selects a value from a string and assigns it to a symbol. The index value (start value) cannot be greater than the length of the string. The format of the directive is:

SUBSTR ,

-or-

SUBSTR, ,

The directive is documented on pages 246-247 of the MASM 6.1x "Programmer[ASCII 146]s Guide."

Sample Code
; Assemble options needed: /c /Fl .model small .data op1 substr ,8 ;  4 op2 sizestr op1         ;  5

op3 substr ,9 ;  7 - should be A2091 here op4 sizestr op3         ;  8 - should be A2006 here

op5 substr ,10 ; 10 - A2091 here op6 sizestr op5         ; 11 - A2006 here END

Assembling this will correctly generate two errors (A2091 and A2006) on lines 10 and 11 as shown in the following (partial) listing. These errors should also be generated on lines 7 and 8 of the source, but aren't, and the value 0 (zero) is incorrectly assigned to symbol op4.

; Assemble options needed: /c /Fl .model small 0000         .data = 8             op1 substr ,8  ;  4 = 0001          op2 sizestr op1          ;  5

=               op3 substr ,9  ;  7 - should be A2091 here = 0000          op4 sizestr op3          ;  8 - should be A2006 here

op5 substr ,10 ; 10 - A2091 here test.asm(10): error A2091: index value past end of string op6 sizestr op5         ; 11 - A2006 here test.asm(11): error A2006: undefined symbol : op5 END

Additional query words: 6.00 6.00a 6.00b 6.10 6.10a buglist6.10 buglist6.10b buglist6.11 buglist6.00 buglist6.00b buglist6.00a

Keywords: KB111502

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