---
name: "mono-shlib-cop"
section: "1"
platform: "linux"
package: "mono"
version: "6.12.0.206-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/mono-shlib-cop"
---

# mono-shlib-cop(1)

Shared Library Usage Checker

## NAME

mono-shlib-cop - Shared Library Usage Checker

## SYNOPSIS

**mono-shlib-cop** \[OPTIONS\]\* \[ASSEMBLY-FILE-NAME\]\*

## OPTIONS

- *-p, --prefixes=PREFIX*

  Mono installation prefixes.  This is to find $prefix/etc/mono/config. The default is based upon the location of mscorlib.dll, and is normally correct.

## DESCRIPTION

*mono-shlib-cop* is a tool that inspects a managed assembly looking for erroneous or suspecious usage of shared libraries.

The tool takes one or more assembly filenames, and inspects each assembly specified.

The errors checked for include:

- \*

  Does the shared library exist?

- \*

  Does the requested symbol exist within the shared library?

The warnings checked for include:

- \*

  Is the target shared library a versioned library?  (Relevant only on Unix systems, not Mac OS X or Windows.)

In general, only versioned libraries such as  *libc.so.6* are present on the  user's machine, and efforts to load  *libc.so* will result in a  **System.DllNotFoundException.** There are three solutions to this:

- 1\.

  Require that the user install any  *-devel* packages which provide the  unversioned library.  This usually requires that the user install a large number of additional packages, complicating the installation process.

- 2\.

  Use a fully versioned name in your  **DllImport** statements.  This requires editing your source code and recompiling whenever you need to target a different version of the shared library.

- 3\.

  Provide an  *assembly.config* file which contains \<dllmap/\> elements to remap the shared library name used by your assembly to the actual versioned shared library present on the users system.  Mono provides a number of pre-existing \<dllmap/\> entries, including ones for  *libc.so* and  *libX11.so.*

## EXAMPLE

The following code contains examples of the above errors and warnings:

```
	using System.Runtime.InteropServices; // for DllImport
	class Demo {
		[DllImport ("bad-library-name")]
		private static extern void BadLibraryName ();
		[DllImport ("libc.so")]
		private static extern void BadSymbolName ();
		[DllImport ("libcap.so")]
		private static extern int cap_clear (IntPtr cap_p);
	}
```

- Bad library name

  Assuming that the library  *bad-library-name* doesn't exist on your machine,  *Demo.BadLibraryName* will generate an error, as it requires a shared library which cannot be loaded. This may be ignorable; see  **BUGS**

- Bad symbol name

  *Demo.BadSymbolName* will generate an error, as  *libc.so* (remapped to  *libc.so.6* by mono's  *$prefix/etc/mono/config* file) doesn't contain the function *BadSymbolName*

- Unversioned library dependency

  Assuming you have the file  *libcap.so* ,  *Demo.cap\_clear* will generate a warning because, while  *libcap.so* could be loaded,  *libcap.so* might not exist on the users machine (on FC2,  */lib/libcap.so* is provided by  *libcap-devel* , and you can't assume that end users will have any  *-devel* packages installed).

## FIXING CODE

The fix depends on the warning or error:

- Bad library names

  Use a valid library name in the  **DllImport** attribute, or provide a \<dllmap/\> entry to map your existing library name to a valid library name.

- Bad symbol names

  Reference a symbol that actually exists in the target library.

- Unversioned library dependency

  Provide a \<dllmap/\> entry to reference a properly versioned library, or ignore the warning (see  **BUGS** ).

## DLLMAP ENTRIES

Mono looks for an *ASSEMBLY-NAME* .config file for each assembly loaded, and reads this file to find Dll mapping information.  For example, with *mcs.exe* , Mono would read  *mcs.exe.config* , and for  *Mono.Posix.dll* , Mono would read  *Mono.Posix.dll.config* .

The  *.config* file is an XML document containing a top-level \<configuration/\> section with nested \<dllmap/\> entries, which contains  **dll** and **target** attributes.  The dll attribute should contain the same string used in your **DllImport** attribute value, and the target attribute specifies which shared library mono should  *actually* load at runtime.

A sample .config file is:

```
	<configuration>
		<dllmap dll="gtkembedmoz" target="libgtkembedmoz.so" />
	</configuration>
```

## BUGS

- \*

  Only  **DllImport** entries are checked; the surrounding IL is ignored.  Consequently, if a runtime check is performed to choose which shared library to invoke, an error will be reported even though the specified library is never used.  Consider this code:

  ```
  	using System.Runtime.InteropServices; // for DllImport
  	class Beep {
  		[DllImport ("kernel32.dll")]
  		private static extern int Beep (int dwFreq, int dwDuration);
  		[DllImport ("libcurses.so")]
  		private static extern int beep ();
  		public static void Beep ()
  		{
  			if (System.IO.Path.DirectorySeparatorChar == '\\') {
  				Beep (750, 300);
  			}
  			else {
  				beep ();
  			}
  		}
  	}
  ```

  If  *mono-shlib-cop* is run on this assembly, an error will be reported for using *kernel32.dll* , even though  *kernel32.dll* will never be used on Unix platforms.

- \*

  *mono-shlib-cop* currently only examines the shared library file extension to determine if a warning should be generated.  A *.so* extension will always generate a warning, even if the  *.so* is not a symlink, isn't provided in a  *-devel* package, and there is no versioned shared library  (possible examples including  */usr/lib/libtcl8.4.so,* */usr/lib/libubsec.so,* etc.).

  Consequently, warnings for any such libraries are useless, and incorrect.

  Windows and Mac OS X will never generate warnings, as these platforms use different shared library extensions.

## MAILING LISTS

Visit http://lists.ximian.com/mailman/listinfo/mono-devel-list for details.

## WEB SITE

Visit http://www.mono-project.com for details