As a follow up of previous post, the issue is confirmed to be located at the prebuilt phase of libsofia_sip_ua_static lib ie at *if not exist "$(ProjectDir)..\..\sofia-sip\win32\gawk.exe" cscript /nologo "$(ProjectDir)..\util.vbs" Get http://files.freeswitch.org/downloads/win32/gawk.exe"$(ProjectDir)..\..\sofia-sip\win32\" cd /D "$(ProjectDir)..\..\sofia-sip\win32\" set AWK="$(ProjectDir)..\..\sofia-sip\win32\gawk.exe" "autogen.cmd"* What seems to happen is that after gawk.exe is loaded, the prebuilt is trying to go on while concurrently the anti-virus/protection is checking the gawk.exe -> this creates a mess and concludes with a failure and then missing headers and so on. *What I've done is simply to preload gawk.exe in the target directory, declared it as safe to the AV/Firewall and only then launch the VS built.* So as a suggestion, loading gawk ahead (ie at thbeginning of the build) could be a way btw. The previous discussed recommendations (changes) related to SDK 7.1 are valid