On 8/2/24 4:18 PM, Patrick Palka wrote:
On Fri, 2 Aug 2024, Patrick Palka wrote:
On Fri, 2 Aug 2024, Jason Merrill wrote:
On 8/1/24 2:52 PM, Patrick Palka wrote:
In recent versions of GCC we've been diagnosing more and more kinds of
errors inside a template ahead of time. This is a largely good thing
because it catches bugs, typos, dead code etc sooner.
But if the template never gets instantiated then such errors are
harmless, and can be inconvenient to work around if say the code in
question is third party and in maintenence mode. So it'd be useful to
"maintenance"
Fixed
diff --git a/gcc/cp/error.cc b/gcc/cp/error.cc
index d80bac822ba..0bb0a482e28 100644
--- a/gcc/cp/error.cc
+++ b/gcc/cp/error.cc
@@ -165,6 +165,58 @@ class cxx_format_postprocessor : public
format_postprocessor
deferred_printed_type m_type_b;
};
+/* A map from TEMPLATE_DECL to the location of the first error (if any)
+ within the template that we permissivly downgraded to a warning. */
"permissively"
Fixed
+relaxed_template_errors_t *relaxed_template_errors;
+
+/* Callback function diagnostic_context::m_adjust_diagnostic_info.
+
+ In -fpermissive mode we downgrade errors within a template to
+ warnings, and only issue an error if we later need to instantiate
+ the template. */
+
+static void
+cp_adjust_diagnostic_info (diagnostic_context *context,
+ diagnostic_info *diagnostic)
+{
+ tree ti;
+ if (diagnostic->kind == DK_ERROR
+ && context->m_permissive
+ && !current_instantiation ()
+ && in_template_context
+ && (ti = get_template_info (current_scope ())))
+ {
+ if (!relaxed_template_errors)
+ relaxed_template_errors = new relaxed_template_errors_t;
+
+ tree tmpl = TI_TEMPLATE (ti);
+ if (!relaxed_template_errors->get (tmpl))
+ relaxed_template_errors->put (tmpl, diagnostic->richloc->get_loc ());
+ diagnostic->kind = DK_WARNING;
Rather than check m_permissive directly and downgrade to DK_WARNING, how about
downgrading to DK_PERMERROR? That way people will get the [-fpermissive]
clue.
...though I suppose DK_PERMERROR doesn't work where you call this hook in
report_diagnostic, at which point we've already reassigned it into DK_WARNING
or DK_ERROR in diagnostic_impl.
But we could still set diagnostic->option_index even for DK_ERROR, whether to
context->m_opt_permissive or to its own warning flag, perhaps
-Wno-template-body?
Fixed by adding an enabled-by-default -Wtemplate-body flag and setting
option_index to it for each downgraded error. Thus -permissive
-Wno-template-body would suppress the downgraded warnings entirely, and
only issue a generic error upon instantiation of the erroneous template.
... or did you have in mind to set option_index even when not using
-fpermissive so that eligible non-downgraded errors get the
[-fpermissive] or [-Wtemplate-body] hint as well?
Yes.
IMHO I'm not sure that'd be worth the extra noise since the vast
majority of users appreciate and expect errors to get diagnosed inside
templates.
But people trying to build legacy code should appreciate the pointer for
how to make it compile, as with other permerrors.
And on second thought I'm not sure what extra value a new warning flag
adds either. I can't think of a good reason why one would use
-fpermissive -Wno-template-body?
One would use -Wno-template-body (or -Wno-error=template-body) without
-fpermissive, like with the various permerror_opt cases.
Jason
