[PATCH] c++ modules: stream non-trailing default targs [PR105045]

[Patrick Palka via Gcc-patches]

This fixes the below testcase in which we neglect to stream the default
argument for T only because the subsequent parameter U doesn't also have
a default argument.

Tested on x86_64-pc-linux-gnu, does this look OK for trunk?

        PR c++/105045

gcc/cp/ChangeLog:

        * module.cc (trees_out::tpl_parms_fini): Don't assume default
        template arguments are all trailing.
        (trees_in::tpl_parms_fini): Likewise.

gcc/testsuite/ChangeLog:

        * g++.dg/modules/pr105045_a.C: New test.
        * g++.dg/modules/pr105045_b.C: New test.
---
 gcc/cp/module.cc                          | 20 ++++++--------------
 gcc/testsuite/g++.dg/modules/pr105045_a.C |  7 +++++++
 gcc/testsuite/g++.dg/modules/pr105045_b.C |  6 ++++++
 3 files changed, 19 insertions(+), 14 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/pr105045_a.C
 create mode 100644 gcc/testsuite/g++.dg/modules/pr105045_b.C

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 999ff3faafc..2c2f9a9a8cb 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -10034,15 +10034,11 @@ trees_out::tpl_parms_fini (tree tmpl, unsigned 
tpl_levels)
       tree vec = TREE_VALUE (parms);
 
       tree_node (TREE_TYPE (vec));
-      tree dflt = error_mark_node;
       for (unsigned ix = TREE_VEC_LENGTH (vec); ix--;)
        {
          tree parm = TREE_VEC_ELT (vec, ix);
-         if (dflt)
-           {
-             dflt = TREE_PURPOSE (parm);
-             tree_node (dflt);
-           }
+         tree dflt = TREE_PURPOSE (parm);
+         tree_node (dflt);
 
          if (streaming_p ())
            {
@@ -10072,19 +10068,15 @@ trees_in::tpl_parms_fini (tree tmpl, unsigned 
tpl_levels)
        tpl_levels--; parms = TREE_CHAIN (parms))
     {
       tree vec = TREE_VALUE (parms);
-      tree dflt = error_mark_node;
 
       TREE_TYPE (vec) = tree_node ();
       for (unsigned ix = TREE_VEC_LENGTH (vec); ix--;)
        {
          tree parm = TREE_VEC_ELT (vec, ix);
-         if (dflt)
-           {
-             dflt = tree_node ();
-             if (get_overrun ())
-               return false;
-             TREE_PURPOSE (parm) = dflt;
-           }
+         tree dflt = tree_node ();
+         if (get_overrun ())
+           return false;
+         TREE_PURPOSE (parm) = dflt;
 
          tree decl = TREE_VALUE (parm);
          if (TREE_CODE (decl) == TEMPLATE_DECL)
diff --git a/gcc/testsuite/g++.dg/modules/pr105045_a.C 
b/gcc/testsuite/g++.dg/modules/pr105045_a.C
new file mode 100644
index 00000000000..597f9294185
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr105045_a.C
@@ -0,0 +1,7 @@
+// PR c++/105045
+// { dg-additional-options -fmodules-ts }
+// { dg-module-cmi pr105045 }
+
+export module pr105045;
+
+export template<int T=0, class U> void f(U) { }
diff --git a/gcc/testsuite/g++.dg/modules/pr105045_b.C 
b/gcc/testsuite/g++.dg/modules/pr105045_b.C
new file mode 100644
index 00000000000..77c94d4c473
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr105045_b.C
@@ -0,0 +1,6 @@
+// PR c++/105045
+// { dg-additional-options -fmodules-ts }
+
+import pr105045;
+
+int main() { f(0); }
-- 
2.38.0.118.g4732897cf0