Hello all,

clang 3.4 is unable to successfully compile Guile 1.8, 2.0, or master.
In all cases, Guile segfaults on its first execution, while trying to
generate guile-procedures.texi.

The reason is that clang 3.4's C preprocessor introduces a lot of extra
newlines in surprising places.  Our snarfing macros are unable to cope
with this, and lots of initialization code is lost.

For example, ports.c contains:

  SCM_VARIABLE (default_conversion_strategy_var,
                "%default-port-conversion-strategy");

Here's the definition of SCM_VARIABLE from snarf.h:

--8<---------------cut here---------------start------------->8---
#define SCM_VARIABLE(c_name, scheme_name) \
SCM_SNARF_HERE(static SCM c_name) \
SCM_SNARF_INIT(c_name = scm_c_define (scheme_name, SCM_BOOL_F);)
--8<---------------cut here---------------end--------------->8---

When guile-snarf is run to generate ports.x, SCM_MAGIC_SNARF_INITS is
defined, so the following definitions are active:

--8<---------------cut here---------------start------------->8---
# define SCM_SNARF_HERE(X)
# define SCM_SNARF_INIT_PREFIX ^^
# define SCM_SNARF_INIT(X) SCM_SNARF_INIT_PREFIX X ^:^
# define SCM_SNARF_DOCS(TYPE, CNAME, FNAME, ARGLIST, REQ, OPT, VAR, DOCSTRING)
--8<---------------cut here---------------end--------------->8---

So you might expect the definition of 'default_conversion_strategy_var'
in ports.c to expand into something like this:

--8<---------------cut here---------------start------------->8---
^^ default_conversion_strategy_var = scm_c_define ("%default-port-conversion-strategy", SCM_BOOL_F); ^:^
--8<---------------cut here---------------end--------------->8---

However, clang -E inserts 6 newlines between the open paren and the open
quote above.  Unfortunately, afaict, the 'sed' script in the
'modern_snarf' function in 'guile-snarf' cannot cope with any newlines
between the "^^" and "^:^".

I've attached a diff between the .x files generated by gcc vs clang.

Any suggestions on how best to fix this?

     Mark