[gcc r14-1870] libcpp: Diagnose #include after failed __has_include [PR80753]

[gcc r14-1870] libcpp: Diagnose #include after failed __has_include [PR80753]

[Jakub Jelinek]

https://gcc.gnu.org/g:37f373e974ac0a272b0e2b24e27c08833ad43470

commit r14-1870-g37f373e974ac0a272b0e2b24e27c08833ad43470
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Jun 15 14:16:17 2023 +0200

    libcpp: Diagnose #include after failed __has_include [PR80753]
    
    As can be seen in the testcase, we don't diagnose #include/#include_next
    of a non-existent header if __has_include/__has_include_next is done for
    that header first.
    The problem is that we normally error the first time some header is not
    found, but in the _cpp_FFK_HAS_INCLUDE case obviously don't want to diagnose
    it, just expand it to 0.  And libcpp caches both successful includes and
    unsuccessful ones.
    
    The following patch fixes that by remembering that we haven't diagnosed
    error when using __has_include* on it, and diagnosing it when using the
    cache entry in normal mode the first time.
    
    I think _cpp_FFK_NORMAL is the only mode in which we normally diagnose
    errors, for _cpp_FFK_PRE_INCLUDE that open_file_failed isn't reached
    and for _cpp_FFK_FAKE neither.
    
    2023-06-15  Jakub Jelinek  <jakub@redhat.com>
    
            PR preprocessor/80753
    libcpp/
            * files.cc (struct _cpp_file): Add deferred_error bitfield.
            (_cpp_find_file): When finding a file in cache with deferred_error
            set in _cpp_FFK_NORMAL mode, call open_file_failed and clear the flag.
            Set deferred_error in _cpp_FFK_HAS_INCLUDE mode if open_file_failed
            hasn't been called.
    gcc/testsuite/
            * c-c++-common/missing-header-5.c: New test.

Diff:
---
 gcc/testsuite/c-c++-common/missing-header-5.c | 15 +++++++++++++++
 libcpp/files.cc                               | 15 ++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/c-c++-common/missing-header-5.c b/gcc/testsuite/c-c++-common/missing-header-5.c
new file mode 100644
index 00000000000..aa36c686d83
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/missing-header-5.c
@@ -0,0 +1,15 @@
+/* PR preprocessor/80753 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+#if __has_include("nonexistent.h")
+# error
+#endif
+
+#include "nonexistent.h"
+
+/* { dg-message "nonexistent.h" "nonexistent.h" { target *-*-* } 0 } */
+/* { dg-message "terminated" "terminated" { target *-*-* } 0 } */
+
+/* This declaration should not receive any diagnostic.  */
+foo bar;
diff --git a/libcpp/files.cc b/libcpp/files.cc
index 3f8a8106ec8..43a8894b7de 100644
--- a/libcpp/files.cc
+++ b/libcpp/files.cc
@@ -109,6 +109,10 @@ struct _cpp_file
   /* If this file is implicitly preincluded.  */
   bool implicit_preinclude : 1;
 
+  /* Set if a header wasn't found with __has_include or __has_include_next
+     and error should be emitted if it is included normally.  */
+  bool deferred_error : 1;
+
   /* > 0: Known C++ Module header unit, <0: known not.  ==0, unknown  */
   int header_unit : 2;
 };
@@ -523,7 +527,14 @@ _cpp_find_file (cpp_reader *pfile, const char *fname, cpp_dir *start_dir,
   cpp_file_hash_entry *entry
     = search_cache ((struct cpp_file_hash_entry *) *hash_slot, start_dir);
   if (entry)
-    return entry->u.file;
+    {
+      if (entry->u.file->deferred_error && kind == _cpp_FFK_NORMAL)
+	{
+	  open_file_failed (pfile, entry->u.file, angle_brackets, loc);
+	  entry->u.file->deferred_error = false;
+	}
+      return entry->u.file;
+    }
 
   _cpp_file *file = make_cpp_file (start_dir, fname);
   file->implicit_preinclude
@@ -589,6 +600,8 @@ _cpp_find_file (cpp_reader *pfile, const char *fname, cpp_dir *start_dir,
 
 	    if (kind != _cpp_FFK_HAS_INCLUDE)
 	      open_file_failed (pfile, file, angle_brackets, loc);
+	    else
+	      file->deferred_error = true;
 	    break;
 	  }