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FAQ
This page contains a list of questions frequently asked about Detours. The questions are grouped by general topic and area of interest.
Yes. Detours is fully compatible with Windows 10 desktop and server applications. While Detours can be used in the development and testing of Window Store apps, new Windows Store apps for Windows 10 can not ship with Detours.
Windows Store apps may use only a subset of the Win32 API. Detours requires several Win32 APIs that are forbidden in for Windows App Certification. Forbidden APIs used by Detours include VirtualAlloc, VirtualProtect, and FlushInstructionCache.
No. Detours is compatible only with the Windows NT family of operating systems: Windows NT, Windows XP, and Windows Server 2003, etc. Detours does not work on the Windows 9x family of operating systems because they have a primitive virtual memory system.
Look in the Detours Samples. The Detours Samples are quite extensive. It is likely that anything you want to accomplish with Detours is covered in one of the included samples.
You need to build a version of detours.lib for your C/C++ compiler. The steps to build detours are:
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Initialize the Microsoft C++ toolset command line environment for the architecture you are targeting.
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Clone the Detours repository:
git clone https://github.com/microsoft/Detours.git -
Build with
nmakea. To build just the detours library, change to the
detours/srcdirectory and run thenmakecommand.b. To build detours and the samples, change to the
detoursdirectory and run thenmakecommand. -
A
lib.<ARCH>directory should now exist, containing the Detours static library, where<ARCH>is the target architecture you are compiling for. Theincludedirectory will also be generated during the build, it contains the headers for the library.C:\detours> dir /b *.x64
bin.X64
lib.X64
C:\detours> dir /b lib.X64
detours.lib
detours.pdb
syelog.lib
C:\detours> dir /b include
detours.h
detver.h
syelog.h
Probably because the target program is not using the malloc function
you detoured.
Standard library functions like malloc can be linked with a program
either statically, from one of the libc*.lib libraries, or
dynamically, from one of the msvcrt*.dll libraries. When statically
linked, a program receives its own private version of the standard
library functions. When dynamically linked, a program shares version of
the standard library functions in a DLL. If you detour your private
version of the function, or if the target program uses its own private
version of the function, your detour won't be called by the target
program.
Why is Detours packaged as a static library (detours.lib) and not as a dynamic link library (say detours.dll)?
Packaging Detours as a statical library minimizes the risk that you will accidentally detour a function required by the Detours package itself and reduces versioning problems. Note that Detours adds only about 16KB when statically linked with your code.
No, the detoured.dll marker file was removed in Detours 3.0. Before
Detours 3.0, this file was used as marker to guide Microsoft technical
support personnel and tools, like Windows Error
Reporting,
by helping them quickly determine that a process has been altered by the
Detours package. Advances in Windows OCA in Windows 7 removed the need
for this marker as Windows 7 maintains a list of DLL that have been
unloaded from a process. Microsoft can not guarantee nor support in any
way, the modification of Microsoft binaries by third parties. Nor can
Microsoft support, in any way, an application that contains Microsoft
binaries modified by third parties. This includes in-memory modification
using the Detours package.
The Windbg can single step or break on exceptions in process startup. Windbg is available in the "Debugging Tools for Windows" download from on msdn.microsoft.com. For example, you can use the command line:
windbg -o withdll.exe -d:mydll.dll myexe.exe
It is also possible to debug child process startup in Visual Studio by using the Microsoft Child Process Debugging Power Tool extension. Once installed you'll need to enable child process debugging using the extension, detailed instructions on how to achieve this can be found in the blog post announcing the extension.
Debuggers insert breakpoints by replacing function code with break
instructions. For example, on the X86 and X64 processors, the debugger
will write a 0xCC (int 3) for a breakpoint. If the breakpoint is written
before a detour is applied, the Detour library will see the 0xCC instead
of the real instructions.
The best way to work around this issue is to ensure that no debugger breakpoints are set on target functions.
Detours is licensed under the MIT license, which allows commercial use.
Please open an issue on the GitHub issue tracker system. In your issue, please be sure to include the version of Detours that are you are using. Before opening an issue, please make every effort to ensure that the problem is not an error in your own code or your usage of Detours. The most common sources of user error are covered in this FAQ.
You can also send detailed bug reports to detours@microsoft.com. Please include the text "DETOURS BUG REPORT" in the subject line. Within the body of your message, please include the first line from the README.TXT file which contains the full description of the version Detours you are using including the Build number.
The detours@microsoft.com email address is for bug reports only, it is
not a product support line.