[tlbuild] dvisvgm-2.1 trial build

[Ken Brown]

On 1/31/2017 7:08 PM, Karl Berry wrote:
> Hello TL builders - I've imported a major new version of dvisvgm (2.1)
> into TeX Live. If you're up for it, feel free to try a build and see how
> it fails :).
>
> I believe that C++ as of 2011 is now required. The configure script checks
> for this and uses, e.g., g++ -std=c++11, when that is supported.

The build succeeds on Cygwin, provided I apply the following patch:

--- source/texk/dvisvgm/configure.ac    (revision 43113)
+++ source/texk/dvisvgm/configure.ac    (working copy)
@@ -32,7 +32,7 @@
  AC_PROG_CC
  AC_PROG_CC_C99
  AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX([11], [noext])
+AX_CXX_COMPILE_STDCXX([11])
  KPSE_CXX_HACK

  AC_PROG_RANLIB

This yields CXX = g++ -std=gnu++11.  Without this change, I get CXX = 
g++ -std=c++11, and the build fails with complaints about M_PI being 
undefined.  Apparently the math constants like M_PI are not defined in 
ISO standard C++, which is implied by -std=c++11.

An alternative that also works is to set

  CXX = g++ -std=c++11 -D_DEFAULT_SOURCE.

Ken