Historically, Spirit supported a lot of compilers, including (to some extent) poorly conforming compilers such as VC6. Spirit v1.6.x will be the last release that will support older poorly conforming compilers. Starting from Spirit v1.8.0, ill conforming compilers will not be supported. If you are still using one of these older compilers, you can still use Spirit v1.6.x.

The reason why Spirit v1.6.x worked on old non-conforming compilers is that the authors laboriously took the trouble of searching for workarounds to make these compilers happy. The process takes a lot of time and energy, especially when one encounters the dreaded ICE or "Internal Compiler Error". Sometimes searching for a single workaround takes days or even weeks. Sometimes, there are no known workarounds. This stifles progress a lot. And, as the library gets more progressive and takes on more advanced C++ techniques, the difficulty is escalated to even new heights.

Spirit v1.6.x will still be supported. Maintenance and bug fixes will still be applied. There will still be active development for the back- porting of new features introduced in Spirit v1.8.0 (and Spirit 1.9.0) to lesser able compilers; hopefully, fueled by contributions from the community. For instance, there is already a working AST tree back-port for VC6 and VC7 by Peder Holt.

This failure is caused by a compiler bug that manifests itself in the particular environment/hardware configuration the test has been run in. You may or may not experience this issue in your local setup.

With GCC 3.4.6 the test fails with ICE: internal compiler error. The footprint is similar to that in GCC Bugzilla Bug 34950 except 34950 is a regression introduced in GCC 4.2.3. In any case, whatever the problem is, the GCC 4.x series does not seem to have it: the test compiles just fine with GCC 4.x compiler.