mono-shlib-cop(1)
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 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
mono-shlib-cop(1)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
