mono-shlib-cop(1)mono-shlib-cop(1)NAMEmono-shlib-cop - Shared Library Usage Checker
SYNOPSISmono-shlib-cop [OPTIONS]* [ASSEMBLY-FILE-NAME]*
OPTIONS-p, --prefixes=PREFIX
Mono installation prefixes. This is to find $pre‐
fix/etc/mono/config. The default is based upon the location of
mscorlib.dll, and is normally correct.
DESCRIPTIONmono-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 assem‐
bly 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 Sys‐
tem.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/> ele‐
ments 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 gen‐
erate a warning because, while libcap.so could be loaded, lib‐
cap.so might not exist on the users machine (on FC2, /lib/lib‐
cap.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 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 <configura‐
tion/> 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 speci‐
fies 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
mono-shlib-cop(1)
