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/Gf, /GF (Eliminate Duplicate Strings)
These options enable the compiler to create a single copy of identical strings in the program image and in memory during execution, resulting in smaller programs, an optimization called string pooling.
- /Gf pools strings as read/write.
- /GF pools strings as read-only.
If you use /GF, the operating system does not swap the string portion of memory and can read the strings back from the image file. If you try to modify strings under /GF, an application error occurs.
If you use /Gf, it is your program's responsibility not to overwrite pooled strings.
Note In the next release of Visual C++, /Gf will be removed from the compiler. You should either remove /Gf from your projects or replace it with /GF. /Gf can cause unexpected behavior if a string that was pooled with another one is written. So, you should not use /Gf if you write to your strings and if you are not writing to your strings, you should use /GF.
String pooling allows what were intended as multiple pointers to multiple buffers to be as multiple pointers to a single buffer. In the following code,
t are initialized with the same string. String pooling causes them to point to the same memory:
char *s = "This is a character buffer"; char *t = "This is a character buffer";
Note The /ZI option, used for Edit and Continue, automatically sets the /GF option. This means that strings will be pooled and placed in read-only memory even if you specify /Gf manually.
/GF is in effect when /O1 or /O2 is used.
To set this compiler option in the Visual Studio development environment
- Open the project's Property Pages dialog box. For details, see Setting Visual C++ Project Properties.
- Click the C/C++ folder.
- Click the Code Generation property page.
- Modify the Enable String Pooling (/GF) property. Set /Gf in the Command Line property page.
To set this compiler option programmatically