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/JMC (Just My Code debugging)

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Specifies compiler support for native Just My Code debugging in the Visual Studio debugger. This option supports the user settings that allow Visual Studio to step over system, framework, library, and other non-user calls, and to collapse those calls in the call stack window. The /JMC compiler option is available starting in Visual Studio 2017 version 15.8.

Syntax

/JMC[-]

Remarks

The Visual Studio Just My Code settings specify whether the Visual Studio debugger steps over system, framework, library, and other non-user calls. The /JMC compiler option enables support for Just My Code debugging in your native C++ code. When /JMC is enabled, the compiler inserts calls to a helper function, __CheckForDebuggerJustMyCode, in the function prolog. The helper function provides hooks that support Visual Studio debugger Just My Code step operations. To enable Just My Code in the Visual Studio debugger, on the menu bar, choose Tools > Options, and then set the option in Debugging > General > Enable Just My Code.

The /JMC option requires that your code links to the C Runtime Library (CRT), which provides the __CheckForDebuggerJustMyCode helper function. If your project doesn't link to the CRT, you may see linker error LNK2019: unresolved external symbol __CheckForDebuggerJustMyCode. To resolve this error, either link to the CRT, or disable the /JMC option.

When the /JMC option is enabled, the PDB file is annotated with extra line number information. In versions before Visual Studio 2019 version 16.8, this information may appear in code coverage reports as occurring at line 15732480 (0xF00F00) or 16707566 (0xFEEFEE). These fictitious line numbers are used as markers to delineate user code from non-user code. To include non-user code in code coverage reports without these unexpected line numbers, build your code with the /JMC- option.

By default, the /JMC compiler option is off. However, starting in Visual Studio 2017 version 15.8 this option is enabled in most Visual Studio project templates. To explicitly disable this option, use the /JMC- option on the command line. In Visual Studio, open the project Property Pages dialog box, and change the Support Just My Code Debugging property in the Configuration Properties > C/C++ > General property page to No.

For more information, see C++ Just My Code in Specify whether to debug only user code using Just My Code in Visual Studio, and the Visual C++ Team Blog post Announcing C++ Just My Code Stepping in Visual Studio.

To set this compiler option in the Visual Studio development environment

  1. Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.

  2. Select the Configuration Properties > C/C++ > General property page.

  3. Modify the Support Just My Code Debugging property.

To set this compiler option programmatically

See also

MSVC compiler options
MSVC compiler command-line syntax