c++/modules: Remove unnecessary errors when not writing compiled module

It was pointed out to me that the current error referencing an internal
linkage entity reads almost like an ICE message, with the message
finishing with the unhelpful:

m.cpp:1:8: error: failed to write compiled module: Bad file data
    1 | export module M;
      |        ^~~~~~

Similarly, whenever we decide not to emit a module CMI due to other
errors we currently emit the following message:

m.cpp:1:8: warning: not writing module ‘M’ due to errors
    1 | export module M;
      |        ^~~~~~

Neither of these messages really add anything useful; users already
understand that when an error is reported then the normal outputs will
not be created, so these messages are just noise.

There is one case we still need this latter message, however; when an
error in a template has been silenced with '-Wno-template-body' we still
don't want to write a module CMI, so emit an error now instead.

This patch also removes a number of dg-prune-output directives in the
testsuite that are no longer needed with this change.

gcc/cp/ChangeLog:

	* module.cc (module_state::write_begin): Return a boolean to
	indicate errors rather than just doing set_error().
	(finish_module_processing): Prevent emission of unnecessary
	errors; only indicate module writing occurred if write_begin
	succeeds.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/export-1.C: Remove message.
	* g++.dg/modules/internal-1.C: Remove message.
	* g++.dg/modules/ambig-2_b.C: Remove unnecessary pruning.
	* g++.dg/modules/atom-decl-2.C: Likewise.
	* g++.dg/modules/atom-pragma-3.C: Likewise.
	* g++.dg/modules/atom-preamble-2_f.C: Likewise.
	* g++.dg/modules/block-decl-2.C: Likewise.
	* g++.dg/modules/dir-only-4.C: Likewise.
	* g++.dg/modules/enum-12.C: Likewise.
	* g++.dg/modules/exp-xlate-1_b.C: Likewise.
	* g++.dg/modules/export-3.C: Likewise.
	* g++.dg/modules/friend-3.C: Likewise.
	* g++.dg/modules/friend-5_b.C: Likewise.
	* g++.dg/modules/inc-xlate-1_e.C: Likewise.
	* g++.dg/modules/linkage-2.C: Likewise.
	* g++.dg/modules/local-extern-1.C: Likewise.
	* g++.dg/modules/main-1.C: Likewise.
	* g++.dg/modules/map-2.C: Likewise.
	* g++.dg/modules/mod-decl-1.C: Likewise.
	* g++.dg/modules/mod-decl-3.C: Likewise.
	* g++.dg/modules/pr99174.H: Likewise.
	* g++.dg/modules/pr99468.H: Likewise.
	* g++.dg/modules/token-1.C: Likewise.
	* g++.dg/modules/token-3.C: Likewise.
	* g++.dg/modules/token-4.C: Likewise.
	* g++.dg/modules/token-5.C: Likewise.
	* g++.dg/modules/using-10.C: Likewise.
	* g++.dg/modules/using-12.C: Likewise.
	* g++.dg/modules/using-3.C: Likewise.
	* g++.dg/modules/using-9.C: Likewise.
	* g++.dg/modules/using-enum-2.C: Likewise.
	* g++.dg/modules/permissive-error-1.C: New test.
	* g++.dg/modules/permissive-error-2.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>

34 files changed, 47 insertions, 68 deletions

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 7c42aea..07477d3 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -3681,7 +3681,7 @@ class GTY((chain_next ("%h.parent"), for_user)) module_state {
 
  public:
   /* Read and write module.  */
-  void write_begin (elf_out *to, cpp_reader *,
+  bool write_begin (elf_out *to, cpp_reader *,
 		    module_state_config &, unsigned &crc);
   void write_end (elf_out *to, cpp_reader *,
 		  module_state_config &, unsigned &crc);
@@ -18317,7 +18317,7 @@ ool_cmp (const void *a_, const void *b_)
      MOD_SNAME_PFX.cfg      : config data
 */
 
-void
+bool
 module_state::write_begin (elf_out *to, cpp_reader *reader,
 			   module_state_config &config, unsigned &crc)
 {
@@ -18395,10 +18395,7 @@ module_state::write_begin (elf_out *to, cpp_reader *reader,
   table.find_dependencies (this);
 
   if (!table.finalize_dependencies ())
-    {
-      to->set_error ();
-      return;
-    }
+    return false;
 
 #if CHECKING_P
   /* We're done verifying at-most once reading, reset to verify
@@ -18595,6 +18592,8 @@ module_state::write_begin (elf_out *to, cpp_reader *reader,
   // so-controlled.
   if (false)
     write_env (to);
+
+  return true;
 }
 
 // Finish module writing after we've emitted all dynamic initializers. 
@@ -20847,20 +20846,29 @@ finish_module_processing (cpp_reader *reader)
 
       cookie = new module_processing_cookie (cmi_name, tmp_name, fd, e);
 
-      if (errorcount
-	  /* Don't write the module if it contains an erroneous template.  */
-	  || (erroneous_templates
-	      && !erroneous_templates->is_empty ()))
-	warning_at (state->loc, 0, "not writing module %qs due to errors",
-		    state->get_flatname ());
+      if (errorcount)
+	/* Don't write the module if we have reported errors.  */;
+      else if (erroneous_templates
+	       && !erroneous_templates->is_empty ())
+	{
+	  /* Don't write the module if it contains an erroneous template.
+	     Also emit notes about where errors occurred in case
+	     -Wno-template-body was passed.  */
+	  auto_diagnostic_group d;
+	  error_at (state->loc, "not writing module %qs due to errors "
+		    "in template bodies", state->get_flatname ());
+	  if (!warn_template_body)
+	    inform (state->loc, "enable %<-Wtemplate-body%> for more details");
+	  for (auto e : *erroneous_templates)
+	    inform (e.second, "first error in %qD appeared here", e.first);
+	}
       else if (cookie->out.begin ())
 	{
-	  cookie->began = true;
-	  auto loc = input_location;
 	  /* So crashes finger-point the module decl.  */
-	  input_location = state->loc;
-	  state->write_begin (&cookie->out, reader, cookie->config, cookie->crc);
-	  input_location = loc;
+	  iloc_sentinel ils = state->loc;
+	  if (state->write_begin (&cookie->out, reader, cookie->config,
+				  cookie->crc))
+	    cookie->began = true;
 	}
 
       dump.pop (n);
diff --git a/gcc/testsuite/g++.dg/modules/ambig-2_b.C b/gcc/testsuite/g++.dg/modules/ambig-2_b.C
index b94416a..859cf14 100644
--- a/gcc/testsuite/g++.dg/modules/ambig-2_b.C
+++ b/gcc/testsuite/g++.dg/modules/ambig-2_b.C
@@ -6,5 +6,3 @@ import A;
 
 extern "C++" int foo ();
 extern "C++" int bar ();  // { dg-error "ambiguating new declaration" }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/atom-decl-2.C b/gcc/testsuite/g++.dg/modules/atom-decl-2.C
index b463dc8..4312015 100644
--- a/gcc/testsuite/g++.dg/modules/atom-decl-2.C
+++ b/gcc/testsuite/g++.dg/modules/atom-decl-2.C
@@ -2,5 +2,3 @@
 export module thing;
 int i;
 import baz; // { dg-error "must be contiguous" }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/atom-pragma-3.C b/gcc/testsuite/g++.dg/modules/atom-pragma-3.C
index b95b2c8..f2cadf0 100644
--- a/gcc/testsuite/g++.dg/modules/atom-pragma-3.C
+++ b/gcc/testsuite/g++.dg/modules/atom-pragma-3.C
@@ -8,5 +8,3 @@ export module foo;
 import baz; // { dg-error "must be contiguous" }
 
 int i;
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/atom-preamble-2_f.C b/gcc/testsuite/g++.dg/modules/atom-preamble-2_f.C
index 28e54b8..42b84af 100644
--- a/gcc/testsuite/g++.dg/modules/atom-preamble-2_f.C
+++ b/gcc/testsuite/g++.dg/modules/atom-preamble-2_f.C
@@ -7,4 +7,3 @@ import kevin; // { dg-error "not be from header" }
 # 8 "" 2
 
 import kevin; // ok
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/block-decl-2.C b/gcc/testsuite/g++.dg/modules/block-decl-2.C
index 974e26f..d491a18 100644
--- a/gcc/testsuite/g++.dg/modules/block-decl-2.C
+++ b/gcc/testsuite/g++.dg/modules/block-decl-2.C
@@ -17,5 +17,3 @@ export extern "C++" auto foo() {
   };
   return X{};
 }
-
-// { dg-prune-output "failed to write compiled module" }
diff --git a/gcc/testsuite/g++.dg/modules/dir-only-4.C b/gcc/testsuite/g++.dg/modules/dir-only-4.C
index 80d6461..9cb0587 100644
--- a/gcc/testsuite/g++.dg/modules/dir-only-4.C
+++ b/gcc/testsuite/g++.dg/modules/dir-only-4.C
@@ -7,4 +7,3 @@ export module foo;
 class import {};
 
 import x; // { dg-error "post-module-declaration" }
- // { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/enum-12.C b/gcc/testsuite/g++.dg/modules/enum-12.C
index cf8f445..3f29c52 100644
--- a/gcc/testsuite/g++.dg/modules/enum-12.C
+++ b/gcc/testsuite/g++.dg/modules/enum-12.C
@@ -6,5 +6,3 @@ export module foo;
 namespace std {
   enum class align_val_t : decltype(sizeof(int)) {};  // { dg-error "in module .foo. conflicts with builtin" }
 }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/exp-xlate-1_b.C b/gcc/testsuite/g++.dg/modules/exp-xlate-1_b.C
index 3295a6a..736e891 100644
--- a/gcc/testsuite/g++.dg/modules/exp-xlate-1_b.C
+++ b/gcc/testsuite/g++.dg/modules/exp-xlate-1_b.C
@@ -4,4 +4,3 @@ export module evil;
 
 export // { dg-error "not part of following" }
 #include "exp-xlate-1_a.H" // { dg-error "must be contiguous" }
-// { dg-prune-output {not writing module} }
diff --git a/gcc/testsuite/g++.dg/modules/export-1.C b/gcc/testsuite/g++.dg/modules/export-1.C
index 5988143..071f5ca 100644
--- a/gcc/testsuite/g++.dg/modules/export-1.C
+++ b/gcc/testsuite/g++.dg/modules/export-1.C
@@ -24,5 +24,3 @@ export class A; // { dg-error "conflicting exporting for declaration" }
 
 template <typename T> struct B;
 export template <typename T> struct B {};  // { dg-error "conflicting exporting for declaration" }
-
-// { dg-warning "due to errors" "" { target *-*-* } 0 }
diff --git a/gcc/testsuite/g++.dg/modules/export-3.C b/gcc/testsuite/g++.dg/modules/export-3.C
index 76765fd..6af314b 100644
--- a/gcc/testsuite/g++.dg/modules/export-3.C
+++ b/gcc/testsuite/g++.dg/modules/export-3.C
@@ -26,5 +26,3 @@ namespace {
 }
 
 export namespace {}  // { dg-error "internal linkage" }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/friend-3.C b/gcc/testsuite/g++.dg/modules/friend-3.C
index 48320eb..cf0bbb7 100644
--- a/gcc/testsuite/g++.dg/modules/friend-3.C
+++ b/gcc/testsuite/g++.dg/modules/friend-3.C
@@ -31,4 +31,3 @@ export void quux (); // { dg-error "conflicting export" }
 void toto (); // not exported
 
 }
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/friend-5_b.C b/gcc/testsuite/g++.dg/modules/friend-5_b.C
index 6b56126..b362cf8 100644
--- a/gcc/testsuite/g++.dg/modules/friend-5_b.C
+++ b/gcc/testsuite/g++.dg/modules/friend-5_b.C
@@ -8,4 +8,3 @@ class B { // { dg-error "conflicts with import" }
   B() { object.value = 42; }
   A object;
 };
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/inc-xlate-1_e.C b/gcc/testsuite/g++.dg/modules/inc-xlate-1_e.C
index f33c464..338c017 100644
--- a/gcc/testsuite/g++.dg/modules/inc-xlate-1_e.C
+++ b/gcc/testsuite/g++.dg/modules/inc-xlate-1_e.C
@@ -1,5 +1,3 @@
 // { dg-additional-options "-fmodules-ts -fmodule-mapper=|@g++-mapper-server\\ -t\\ [srcdir]/inc-xlate-1.map" }
 export module bad;
 #include "inc-xlate-1_a.H"  // { dg-error "not be include-translated" }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/internal-1.C b/gcc/testsuite/g++.dg/modules/internal-1.C
index 45d3bf0..9f7299a 100644
--- a/gcc/testsuite/g++.dg/modules/internal-1.C
+++ b/gcc/testsuite/g++.dg/modules/internal-1.C
@@ -1,6 +1,6 @@
 // { dg-additional-options "-fmodules-ts" }
 
-export module frob; // { dg-error "failed to write" }
+export module frob;
 // { dg-module-cmi !frob }
 
 namespace {
diff --git a/gcc/testsuite/g++.dg/modules/linkage-2.C b/gcc/testsuite/g++.dg/modules/linkage-2.C
index d913d6a..4b20411 100644
--- a/gcc/testsuite/g++.dg/modules/linkage-2.C
+++ b/gcc/testsuite/g++.dg/modules/linkage-2.C
@@ -28,5 +28,3 @@ export void use() {
 // here is an exposure of this type, so this should be an error; we don't yet
 // implement this checking however.
 struct {} s;  // { dg-error "TU-local" "" { xfail *-*-* } }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/local-extern-1.C b/gcc/testsuite/g++.dg/modules/local-extern-1.C
index 7b01605..3e10c67 100644
--- a/gcc/testsuite/g++.dg/modules/local-extern-1.C
+++ b/gcc/testsuite/g++.dg/modules/local-extern-1.C
@@ -15,6 +15,3 @@ inline void dob ()
 {
   extern int bob; // { dg-error "block-scope extern" }
 }
-
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/main-1.C b/gcc/testsuite/g++.dg/modules/main-1.C
index 0d79edd..4292977 100644
--- a/gcc/testsuite/g++.dg/modules/main-1.C
+++ b/gcc/testsuite/g++.dg/modules/main-1.C
@@ -1,5 +1,4 @@
 // { dg-additional-options "-fmodules-ts" }
-// { dg-prune-output "not writing module" }
 
 export module M;
 int main() {}  // { dg-error "attach" }
diff --git a/gcc/testsuite/g++.dg/modules/map-2.C b/gcc/testsuite/g++.dg/modules/map-2.C
index dceb183..94d3f7a 100644
--- a/gcc/testsuite/g++.dg/modules/map-2.C
+++ b/gcc/testsuite/g++.dg/modules/map-2.C
@@ -7,5 +7,3 @@
 export module foo;
 // { dg-error "Interface: no such module" "" { target *-*-* } .-1 }
 // { dg-error "failed reading mapper" "" { target *-*-* } 0 }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/mod-decl-1.C b/gcc/testsuite/g++.dg/modules/mod-decl-1.C
index df398b3..ac7bb84 100644
--- a/gcc/testsuite/g++.dg/modules/mod-decl-1.C
+++ b/gcc/testsuite/g++.dg/modules/mod-decl-1.C
@@ -27,5 +27,3 @@ void Bink ()
 
 module a.; // { dg-error "only permitted as" }
 
-// { dg-prune-output "not writing module" }
-
diff --git a/gcc/testsuite/g++.dg/modules/mod-decl-3.C b/gcc/testsuite/g++.dg/modules/mod-decl-3.C
index 16fa5a8..23ba7f1 100644
--- a/gcc/testsuite/g++.dg/modules/mod-decl-3.C
+++ b/gcc/testsuite/g++.dg/modules/mod-decl-3.C
@@ -22,5 +22,3 @@ namespace Bink
   import  // { dg-error "does not name" }
   ben;
 }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/permissive-error-1.C b/gcc/testsuite/g++.dg/modules/permissive-error-1.C
new file mode 100644
index 0000000..70ae1ec
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/permissive-error-1.C
@@ -0,0 +1,10 @@
+// { dg-additional-options "-fmodules-ts -fpermissive" }
+// { dg-module-cmi !M }
+
+export module M;  // { dg-error "not writing module" }
+
+template <typename T> void f() {
+  const int n = 42;
+  ++n;  // { dg-warning "read-only" }
+	// { dg-message "appeared here" "" { target *-*-* } .-1 }
+}
diff --git a/gcc/testsuite/g++.dg/modules/permissive-error-2.C b/gcc/testsuite/g++.dg/modules/permissive-error-2.C
new file mode 100644
index 0000000..1e62d45
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/permissive-error-2.C
@@ -0,0 +1,11 @@
+// { dg-additional-options "-fmodules-ts -Wno-template-body" }
+// { dg-module-cmi !M }
+
+export module M;  // { dg-error "not writing module" }
+
+template <typename T> void f() {
+  const int n = 42;
+  ++n;  // { dg-message "appeared here" }
+}
+
+// { dg-message "enable \[^\n\r\]* for more details" "" { target *-*-* } 0 }
diff --git a/gcc/testsuite/g++.dg/modules/pr99174.H b/gcc/testsuite/g++.dg/modules/pr99174.H
index 62d5513..60d01c5 100644
--- a/gcc/testsuite/g++.dg/modules/pr99174.H
+++ b/gcc/testsuite/g++.dg/modules/pr99174.H
@@ -1,5 +1,3 @@
 // { dg-additional-options -fmodule-header }
 // { dg-module-cmi !{} }
 import "pr99174.H"; // { dg-error "cannot import" }
-
-// { dg-prune-output {not writing module} }
diff --git a/gcc/testsuite/g++.dg/modules/pr99468.H b/gcc/testsuite/g++.dg/modules/pr99468.H
index b6be0c3..d7da3a8 100644
--- a/gcc/testsuite/g++.dg/modules/pr99468.H
+++ b/gcc/testsuite/g++.dg/modules/pr99468.H
@@ -4,4 +4,3 @@
 module M; // { dg-error "module-declaration not permitted" }
 
 int i;
-// { dg-prune-output "not writing" }
diff --git a/gcc/testsuite/g++.dg/modules/token-1.C b/gcc/testsuite/g++.dg/modules/token-1.C
index 50eee4c..db9a09b 100644
--- a/gcc/testsuite/g++.dg/modules/token-1.C
+++ b/gcc/testsuite/g++.dg/modules/token-1.C
@@ -4,4 +4,3 @@ module ; // { dg-error "cannot be in included file" }
 export module bob; // { dg-error "cannot be in included file" }
 # 6 "" 2
 // { dg-module-cmi !bob }
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/token-3.C b/gcc/testsuite/g++.dg/modules/token-3.C
index 5bab426..1b4f66e 100644
--- a/gcc/testsuite/g++.dg/modules/token-3.C
+++ b/gcc/testsuite/g++.dg/modules/token-3.C
@@ -3,4 +3,3 @@
 export module bob; // { dg-error "in included file" }
 # 6 "" 2
 // { dg-module-cmi !bob }
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/token-4.C b/gcc/testsuite/g++.dg/modules/token-4.C
index 5a85237..388da10 100644
--- a/gcc/testsuite/g++.dg/modules/token-4.C
+++ b/gcc/testsuite/g++.dg/modules/token-4.C
@@ -2,4 +2,3 @@
 #define MODULE module   // { dg-error "does not name a type" }
 export MODULE bob; // { dg-error "may only occur after" }
 // { dg-module-cmi !bob }
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/token-5.C b/gcc/testsuite/g++.dg/modules/token-5.C
index 29d3ec8..8190f5e 100644
--- a/gcc/testsuite/g++.dg/modules/token-5.C
+++ b/gcc/testsuite/g++.dg/modules/token-5.C
@@ -7,4 +7,3 @@ class Y;
 
 export module frob;
 // { dg-module-cmi !frob }
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/using-10.C b/gcc/testsuite/g++.dg/modules/using-10.C
index 5735353..d468a36 100644
--- a/gcc/testsuite/g++.dg/modules/using-10.C
+++ b/gcc/testsuite/g++.dg/modules/using-10.C
@@ -67,5 +67,3 @@ namespace t {
 export using t::a;  // { dg-error "does not have external linkage" }
 export using t::b;  // { dg-error "does not have external linkage" }
 export using t::c;  // { dg-error "does not have external linkage" }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/using-12.C b/gcc/testsuite/g++.dg/modules/using-12.C
index 54eacf7..52ef3c6 100644
--- a/gcc/testsuite/g++.dg/modules/using-12.C
+++ b/gcc/testsuite/g++.dg/modules/using-12.C
@@ -69,5 +69,3 @@ namespace t {
   export using t::b;  // { dg-error "does not have external linkage" }
   export using t::c;  // { dg-error "does not have external linkage" }
 }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/using-3.C b/gcc/testsuite/g++.dg/modules/using-3.C
index d21512f..898618d 100644
--- a/gcc/testsuite/g++.dg/modules/using-3.C
+++ b/gcc/testsuite/g++.dg/modules/using-3.C
@@ -13,5 +13,3 @@ using N::bar;
 
 export using N::foo; // { dg-error "does not have external linkage" }
 export using N::bar; // { dg-error "does not have external linkage" }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/using-9.C b/gcc/testsuite/g++.dg/modules/using-9.C
index 4290280..8fb7b5e 100644
--- a/gcc/testsuite/g++.dg/modules/using-9.C
+++ b/gcc/testsuite/g++.dg/modules/using-9.C
@@ -9,5 +9,3 @@ namespace outer {
 }
 
 export using outer::any_of;  // { dg-error "does not have external linkage" }
-
-// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/using-enum-2.C b/gcc/testsuite/g++.dg/modules/using-enum-2.C
index 813e2f6..12e3775 100644
--- a/gcc/testsuite/g++.dg/modules/using-enum-2.C
+++ b/gcc/testsuite/g++.dg/modules/using-enum-2.C
@@ -19,5 +19,3 @@ export using enum s::e1;  // { dg-error "does not have external linkage" }
 export using enum s::e2;  // { dg-error "does not have external linkage" }
 export using enum m::e3;  // { dg-error "does not have external linkage" }
 export using enum m::e4;  // { dg-error "does not have external linkage" }
-
-// { dg-prune-output "not writing module" }