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MAV when run with 9.0.0 runtime, but not 8.1.2.1

  • March 21, 2011
  • 4 replies
  • 0 views
Christopher Ryan

[Migrated content. Thread originally posted on 21 March 2011]

We have a program that queries user32.dll to determine the computer's DPI settings, using the "GetDeviceCaps" function. The following code works fine when run with the 8.1.2.1 runtime, but gives a MAV when run with the version 9.0.0 runtime (compiled by the 8.1.2.1 compiler). The MAV occurs on the call to "ReleaseDC", and does not happen if you step over (skip) the line in the debugger, or if you comment that line out.

           SET ENVIRONMENT "DLL_CONVENTION" TO "1"
           CALL "USER32.DLL@WINAPI"
           CALL "GetDC" Using BY VALUE hwnd GIVING hdc
           CANCEL "user32.dll"
           CALL "gdi32.dll"
           CALL "GetDeviceCaps"
              USING BY VALUE hdc
              BY VALUE LOGPIXELSX
              GIVING DPIX
           END-CALL.
           CALL "GetDeviceCaps"
              USING BY VALUE hdc
              BY VALUE LOGPIXELSY
              GIVING DPIY
           END-CALL.
           CANCEL "gdi32.dll".
           CALL "USER32.DLL@WINAPI"
           CALL "ReleaseDC" Using BY VALUE hdc
           CANCEL "user32.dll"

    4 replies

    Stephen Hjerpe
    • Stephen Hjerpe
    • Participating Frequently
    • March 21, 2011

    [Migrated content. Thread originally posted on 21 March 2011]

    We have a program that queries user32.dll to determine the computer's DPI settings, using the "GetDeviceCaps" function. The following code works fine when run with the 8.1.2.1 runtime, but gives a MAV when run with the version 9.0.0 runtime (compiled by the 8.1.2.1 compiler). The MAV occurs on the call to "ReleaseDC", and does not happen if you step over (skip) the line in the debugger, or if you comment that line out.

               SET ENVIRONMENT "DLL_CONVENTION" TO "1"
               CALL "USER32.DLL@WINAPI"
               CALL "GetDC" Using BY VALUE hwnd GIVING hdc
               CANCEL "user32.dll"
               CALL "gdi32.dll"
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSX
                  GIVING DPIX
               END-CALL.
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSY
                  GIVING DPIY
               END-CALL.
               CANCEL "gdi32.dll".
               CALL "USER32.DLL@WINAPI"
               CALL "ReleaseDC" Using BY VALUE hdc
               CANCEL "user32.dll"
    I believe there is an issue with the 9.0 compiler and the @ symbol, please raise this issue with Customer Care so that it can be addressed.
    Christopher Ryan
    • Christopher Ryan
    • Author
    • Participating Frequently
    • March 21, 2011

    [Migrated content. Thread originally posted on 21 March 2011]

    We have a program that queries user32.dll to determine the computer's DPI settings, using the "GetDeviceCaps" function. The following code works fine when run with the 8.1.2.1 runtime, but gives a MAV when run with the version 9.0.0 runtime (compiled by the 8.1.2.1 compiler). The MAV occurs on the call to "ReleaseDC", and does not happen if you step over (skip) the line in the debugger, or if you comment that line out.

               SET ENVIRONMENT "DLL_CONVENTION" TO "1"
               CALL "USER32.DLL@WINAPI"
               CALL "GetDC" Using BY VALUE hwnd GIVING hdc
               CANCEL "user32.dll"
               CALL "gdi32.dll"
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSX
                  GIVING DPIX
               END-CALL.
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSY
                  GIVING DPIY
               END-CALL.
               CANCEL "gdi32.dll".
               CALL "USER32.DLL@WINAPI"
               CALL "ReleaseDC" Using BY VALUE hdc
               CANCEL "user32.dll"
    GMCfourX4 originally wrote:
    compiled by the 8.1.2.1 compiler


    We have not compiled anything under version 9. This is just replacing the runtime and running our existing code (compiled under version 8) with the new runtime.

    -Chris
    D

    [Migrated content. Thread originally posted on 21 March 2011]

    We have a program that queries user32.dll to determine the computer's DPI settings, using the "GetDeviceCaps" function. The following code works fine when run with the 8.1.2.1 runtime, but gives a MAV when run with the version 9.0.0 runtime (compiled by the 8.1.2.1 compiler). The MAV occurs on the call to "ReleaseDC", and does not happen if you step over (skip) the line in the debugger, or if you comment that line out.

               SET ENVIRONMENT "DLL_CONVENTION" TO "1"
               CALL "USER32.DLL@WINAPI"
               CALL "GetDC" Using BY VALUE hwnd GIVING hdc
               CANCEL "user32.dll"
               CALL "gdi32.dll"
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSX
                  GIVING DPIX
               END-CALL.
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSY
                  GIVING DPIY
               END-CALL.
               CANCEL "gdi32.dll".
               CALL "USER32.DLL@WINAPI"
               CALL "ReleaseDC" Using BY VALUE hdc
               CANCEL "user32.dll"
    Looks like you're missing a parameter to ReleaseDC, according to the MSDN description.

    I ran your code and got the same results (MAV) using the 9.0 runtime (same result whether compiling with 8.1 or 9.0). And, like you, it worked fine with the 8.1 runtime.

    One question is why it worked with 8.1 when it really shouldn't have.

    But by adding the missing parameter, it works fine with 9.0 for me:

               CALL "ReleaseDC" Using
                       BY VALUE hwnd
                       BY VALUE hdc

               if return-code = 1          | ReleaseDC succeeded
                  ...
               else                        | ReleaseDC failed
                  ...
               end-if
    Christopher Ryan
    • Christopher Ryan
    • Author
    • Participating Frequently
    • March 22, 2011

    [Migrated content. Thread originally posted on 21 March 2011]

    We have a program that queries user32.dll to determine the computer's DPI settings, using the "GetDeviceCaps" function. The following code works fine when run with the 8.1.2.1 runtime, but gives a MAV when run with the version 9.0.0 runtime (compiled by the 8.1.2.1 compiler). The MAV occurs on the call to "ReleaseDC", and does not happen if you step over (skip) the line in the debugger, or if you comment that line out.

               SET ENVIRONMENT "DLL_CONVENTION" TO "1"
               CALL "USER32.DLL@WINAPI"
               CALL "GetDC" Using BY VALUE hwnd GIVING hdc
               CANCEL "user32.dll"
               CALL "gdi32.dll"
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSX
                  GIVING DPIX
               END-CALL.
               CALL "GetDeviceCaps"
                  USING BY VALUE hdc
                  BY VALUE LOGPIXELSY
                  GIVING DPIY
               END-CALL.
               CANCEL "gdi32.dll".
               CALL "USER32.DLL@WINAPI"
               CALL "ReleaseDC" Using BY VALUE hdc
               CANCEL "user32.dll"
    Chuck,
    Good catch. It does look like it should not have worked under version 8 either.

    Thank you!
    -Chris

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