/Zm (Specify Precompiled Header Memory Allocation Limit)

Determines the amount of memory that the compiler allocates to construct precompiled headers.



  • factor
    A scaling factor that determines the amount of memory that the compiler uses to construct precompiled headers.

    The factor argument is a percentage of the default size of a compiler-defined work buffer. The default value of the factor argument is 100 (percent), but you can specify larger or smaller amounts.


In earlier versions of Visual C++, the compiler used several discrete heaps, and each had a finite limit. Currently, the compiler dynamically grows the heaps as necessary up to a total heap size limit, and requires a fixed-size buffer only to construct precompiled headers. Consequently, the /Zm compiler option is rarely necessary.

If the compiler runs out of heap space and emits the C1060 error message when you use the /Zm compiler option, you might have reserved too much memory. Consider removing the /Zm option. If the compiler emits the C1076 error message, an accompanying C3859 message specifies the factor argument that you should use when you recompile your program with the /Zm compiler option.

The following table shows how the factor argument affects the memory allocation limit if you assume the size of the default precompiled header buffer is 75 MB.

Value of factor

Memory allocation limit


7.5 MB


75 MB


150 MB


750 MB


1500 MB

Other Ways to Set the Memory Allocation Limit

To set the /Zm compiler option in the Visual Studio development environment

  1. Open the project's Property Pages dialog box. For details, see How to: Open Project Property Pages.

  2. Click the C/C++ folder.

  3. Click the Command Line property page.

  4. Type the compiler option in the Additional Options box.

To set the /Zm compiler option programmatically

See Also


Compiler Options

Setting Compiler Options