Compile on Windows CMake issue

[joesulewski]

Hello,

I'm attempting to compile tcpdump on Windows 11 using version 1.13 of the NPCap SDK and Visual Studio 17 2022. I'm getting an error that libpcap is too old; 1.0 or later is required but I'm using the 1.13 version of the SDK.

I looked at the pcap.h file and it has the following:

PCAP_AVAILABLE_1_0
PCAP_API pcap_t *pcap_create(const char *, char *);

PCAP_AVAILABLE_1_0
PCAP_API const char *pcap_statustostr(int);

Thank you for any help you can offer.

 I issue the following command:
cmake "-DPCAP_ROOT=\development\npcap-sdk-1-13" -G "Visual Studio 17 2022" -A Win32 ..

And I receive the following output:
-- The C compiler identification is MSVC 19.41.34120.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.41.34120/bin/Hostx64/x86/cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Building 32-bit
-- Use DYNAMIC runtime
-- Looking for sys/types.h
-- Looking for sys/types.h - found
-- Looking for stdint.h
-- Looking for stdint.h - found
-- Looking for stddef.h
-- Looking for stddef.h - found
-- Check size of time_t
-- Check size of time_t - done
-- Looking for rpc/rpc.h
-- Looking for rpc/rpc.h - not found
-- Looking for strlcat
-- Looking for strlcat - not found
-- Looking for strlcpy
-- Looking for strlcpy - not found
-- Looking for strsep
-- Looking for strsep - not found
-- Looking for gethostbyaddr
-- Looking for gethostbyaddr - found
-- Looking for getservent
-- Looking for getservent - not found
-- Looking for getservent
-- Looking for getservent - not found
-- Skipped SUITABLE_SNPRINTF because cross-compiling.
-- Looking for getopt_long
-- Looking for getopt_long - not found
-- Looking for getrpcbynumber
-- Looking for getrpcbynumber - not found
-- Looking for getrpcbynumber
-- Looking for getrpcbynumber - not found
-- Looking for ether_ntohost
-- Looking for ether_ntohost - not found
-- Found PCAP: //development/npcap-sdk-1-13/include
-- Looking for pcap/pcap-inttypes.h
-- Looking for pcap/pcap-inttypes.h - not found
-- Looking for pcap_create
-- Looking for pcap_create - not found
CMake Error at CMakeLists.txt:778 (MESSAGE):
libpcap is too old; 1.0 or later is required

-- Configuring incomplete, errors occurred!

[joesulewski]

(formatting applied to display the slashes correctly -- Denis)

Okay, I found the issue. On windows you have to use forward slashes for the CMake comand prompt. For example:

cmake -DPCAP_ROOT=/development/npcap-sdk-1-13 -G "Visual Studio 17 2022" -A Win32 /development/tcpdump

do not use double backslashes like so

cmake -DPCAP_ROOT=\\development\\npcap-sdk-1-13 -G "Visual Studio 17 2022" -A Win32 /development/tcpdump

I'm just getting back to C++ so if this seems obvious my apologies.

[guyharris]

On windows you have to use forward slashes for the CMake comand prompt.

That's hyper-spectacularly broken. I'll try to figure out what needs to be done to fix that.

[infrastation]

It seems possible that CMake takes both slashes and backslashes as valid input and then converts as is necessary for the OS (note the C:/Program Files/ above), but the \\ at the beginning of the path makes it treat the path as a Windows network resource, which then fails. I do not have an environment to confirm this.

[guyharris]

I'm not seeing that problem on my Windows 11 VM.

I followed the instructions at https://github.com/the-tcpdump-group/tcpdump/blob/master/doc/README.windows.md, in an "x64 Native Tools Command Prompt for VS 2022" window. Those instructions use single backslashes, not double backslashes.

[guyharris]

On a side note, your documentation for Windows should include defining PCAP_INCLUDE_DIR and the PCAP_LIBRARY in addition to PCAP_ROOT.

Why? In my tests, it worked without that; the CMake script itself sets those. (find_path(), in CMake 3.12 and later, will, when searching for a package with a given name, search in the appropriate subdirectory of the {package name}_ROOT directory. We require CMake 3.12 and later on Windows.)

[joesulewski]

On a side note, your documentation for Windows should include defining PCAP_INCLUDE_DIR and the PCAP_LIBRARY in addition to PCAP_ROOT.

Why? In my tests, it worked without that; the CMake script itself sets those. (find_path(), in CMake 3.12 and later, will, when searching for a package with a given name, search in the appropriate subdirectory of the {package name}_ROOT directory. We require CMake 3.12 and later on Windows.)

Guy,

I should have removed that from my original comment. I was using \ and cmake doesn't throw errors, it actually tells you it can't find PCAP_INCLUDE_DIR and PCAP_LIBRARY which I interpreted as needing to be added. I'll edit the comment and remove it.
THanks for all the help!

[joesulewski]

I'm not seeing that problem on my Windows 11 VM.

I followed the instructions at https://github.com/the-tcpdump-group/tcpdump/blob/master/doc/README.windows.md, in an "x64 Native Tools Command Prompt for VS 2022" window. Those instructions use single backslashes, not double backslashes.

Guy,

I just looked at the directions and the only reference I see to slashes is in the Visual Studio 2017 GUI section where it says to use double backslashes, not forward slashes. Perhaps I'm missing something, but I don't see any examples or explanation that on the commandline to use forward slashes when defining the PCAP_ROOT variable.

Thanks,