From 3f8a59a05c7d2c65020bd2a756d2c6d5a196bec2 Mon Sep 17 00:00:00 2001
From: Ben Boeckel <ben.boeckel@kitware.com>
Date: Wed, 14 Feb 2024 20:25:53 -0500
Subject: cxxmodules: return failure from the collator when private usage is
 found

---
 Source/cmCxxModuleMapper.cxx      | 3 ++-
 Source/cmCxxModuleMapper.h        | 2 +-
 Source/cmGlobalNinjaGenerator.cxx | 8 +++++++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/Source/cmCxxModuleMapper.cxx b/Source/cmCxxModuleMapper.cxx
index f45c011..b6b9540 100644
--- a/Source/cmCxxModuleMapper.cxx
+++ b/Source/cmCxxModuleMapper.cxx
@@ -305,7 +305,7 @@ cm::static_string_view CxxModuleMapExtension(
 
 std::set<std::string> CxxModuleUsageSeed(
   CxxModuleLocations const& loc, std::vector<cmScanDepInfo> const& objects,
-  CxxModuleUsage& usages)
+  CxxModuleUsage& usages, bool& private_usage_found)
 {
   // Track inner usages to populate usages from internal bits.
   //
@@ -334,6 +334,7 @@ std::set<std::string> CxxModuleUsageSeed(
           cmStrCat("Unable to use module '", r.LogicalName,
                    "' as it is 'PRIVATE' and therefore not accessible outside "
                    "of its owning target."));
+        private_usage_found = true;
         continue;
       }
 
diff --git a/Source/cmCxxModuleMapper.h b/Source/cmCxxModuleMapper.h
index 34111f7..c785099 100644
--- a/Source/cmCxxModuleMapper.h
+++ b/Source/cmCxxModuleMapper.h
@@ -93,7 +93,7 @@ cm::static_string_view CxxModuleMapExtension(
 // import cycle).
 std::set<std::string> CxxModuleUsageSeed(
   CxxModuleLocations const& loc, std::vector<cmScanDepInfo> const& objects,
-  CxxModuleUsage& usages);
+  CxxModuleUsage& usages, bool& private_usage_found);
 
 // Return the contents of the module map in the given format for the
 // object file.
diff --git a/Source/cmGlobalNinjaGenerator.cxx b/Source/cmGlobalNinjaGenerator.cxx
index 22fd90d..b74ba37 100644
--- a/Source/cmGlobalNinjaGenerator.cxx
+++ b/Source/cmGlobalNinjaGenerator.cxx
@@ -2719,7 +2719,9 @@ bool cmGlobalNinjaGenerator::WriteDyndepFile(
 
     // Insert information about the current target's modules.
     if (modmap_fmt) {
-      auto cycle_modules = CxxModuleUsageSeed(locs, objects, usages);
+      bool private_usage_found = false;
+      auto cycle_modules =
+        CxxModuleUsageSeed(locs, objects, usages, private_usage_found);
       if (!cycle_modules.empty()) {
         cmSystemTools::Error(
           cmStrCat("Circular dependency detected in the C++ module import "
@@ -2727,6 +2729,10 @@ bool cmGlobalNinjaGenerator::WriteDyndepFile(
                    cmJoin(cycle_modules, R"(", ")"_s), '"'));
         return false;
       }
+      if (private_usage_found) {
+        // Already errored in the function.
+        return false;
+      }
     }
 
     cmNinjaBuild build("dyndep");
-- 
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