While working with GCC's language hooks, we found that
certain places in GCC test for a null value of
lang_hooks.callgraph.expand_function, but
cgraph_expand_function() calls the hook directly:
In cgraphunit.c:
/* Expand function specified by NODE. */
static void
cgraph_expand_function (struct cgraph_node *node)
{
tree decl = node->decl;
/* We ought to not compile any inline clones. */
gcc_assert (!node->global.inlined_to);
if (flag_unit_at_a_time)
announce_function (decl);
cgraph_lower_function (node);
/* Generate RTL for the body of DECL. */
lang_hooks.callgraph.expand_function (decl);
------------
In toplev.c:
/* Disable unit-at-a-time mode for frontends not supporting callgraph
interface. */
if (flag_unit_at_a_time && ! lang_hooks.callgraph.expand_function)
flag_unit_at_a_time = 0;
------------
In function.c:
/* Possibly warn about unused parameters.
When frontend does unit-at-a-time, the warning is already
issued at finalization time. */
if (warn_unused_parameter
&& !lang_hooks.callgraph.expand_function)
do_warn_unused_parameter (current_function_decl);
------------
We tried setting lang_hooks.callgraph.expand_function to NULL:
/* For now, disable unit-at-a-time by setting expand_function to NULL */
#undef LANG_HOOKS_CALLGRAPH_EXPAND_FUNCTION
#define LANG_HOOKS_CALLGRAPH_EXPAND_FUNCTION NULL
which has the desited effect of disabling unit-at-a-time, but
runs aground in cgraph_expand_function() with a segfault,
when it attempts to call lang_hooks.callgraph.expand_function().
It seems that GCC is handling lang_hooks.callgraph.expand_function
in an inconsistent fashion. Is a null value for expand_function
meaningful? If it is, then what is the fix for cgraph_expand_function()?
