New utility object, StripCtrlChars.

This is for sanitising output that's going to be sent to a terminal,
if you don't want it to be able to send arbitrary escape sequences and
thereby (for example) move the cursor back up to existing text on the
screen and overprint it confusingly.

It works using the standard C library: we convert to a wide-character
string and back, and then use wctype.h to spot control characters in
the intermediate form. This means its idea of the conversion character
set is locale-based rather than any of our own charset library's fixed
settings - which is what you want if the aim is to protect your local
terminal (which we assume the system locale represents accurately).

This also means that the sanitiser strips things that will _act_ as
control characters when sent to the local terminal, whether or not
they were intended as control characters by a server that might have
had a different character set in mind. Since the main aim is to
protect the local terminal rather than to faithfully replicate the
server's intention, I think that's the right criterion.

It only strips control characters at the charset-independent layer,
like backspace, carriage return and the escape character: wctype.h
classifies those as control characters, but classifies as printing all
of the more Unicode-specific controls like bidirectional overrides.
But that's enough to prevent cursor repositioning, for example.

stripctrl.c comes with a test main() of its own, which I wasn't able
to fold into testcrypt and put in the test suite because of its
dependence on the system locale - it wouldn't be guaranteed to work
the same way on different test systems anyway.

A knock-on build tweak: because you can feed data into this sanitiser
in chunks of arbitrary size, including partial multibyte chars, I had
to use mbrtowc() for the decoding, and that means that in the 'old'
Win32 builds I have to link against the Visual Studio C++ library as
well as the C library, because for some reason that's where mbrtowc
lived in VS2003.

1 files changed, 1 insertions, 1 deletions

diff --git a/Buildscr b/Buildscr
index 36b9d3e3..83083f96 100644
--- a/Buildscr
+++ b/Buildscr
@@ -186,7 +186,7 @@ in putty/windows with clangcl_a64 do mkdir abuild64 && Platform=arm64 make -f Ma
 # a subsystem version of 4.0, and compile with /arch:IA32 to prevent
 # the use of modern CPU features like MMX which older machines also
 # might not have.
-in putty/windows with clangcl32_2003 do mkdir buildold && Platform=x86 make -f Makefile.clangcl BUILDDIR=buildold/ $(Makeargs) CCTARGET=i386-pc-windows-msvc13.0.0 SUBSYSVER=,4.0 EXTRA_windows=wincrt0.obj EXTRA_console=crt0.obj XFLAGS=/arch:IA32 all -j$(nproc)
+in putty/windows with clangcl32_2003 do mkdir buildold && Platform=x86 make -f Makefile.clangcl BUILDDIR=buildold/ $(Makeargs) CCTARGET=i386-pc-windows-msvc13.0.0 SUBSYSVER=,4.0 EXTRA_windows=wincrt0.obj EXTRA_console=crt0.obj EXTRA_libs=libcpmt.lib XFLAGS=/arch:IA32 all -j$(nproc)
 
 # Remove Windows binaries for the test programs we don't want to ship,
 # like testbn.exe. (But we still _built_ them, to ensure the build