Fortran: Improve -Wmissing-include-dirs warnings [PR55534]

It turned out that enabling the -Wmissing-include-dirs for libcpp did output
too many warnings – at least as run with -B and similar options during the
GCC build and warning for internal include dirs like finclude, unlikely of
relevance to for a real-world user.
This patch now only warns for -I and -J by default but permits to get the
full warnings including libcpp ones with -Wmissing-include-dirs. It
additionally documents this in the manual.

With that change, the -Wno-missing-include-dirs could be removed
from libgfortran's configure and libgomp's testsuite always cflags.
This reverts those bits of the previous
commit r12-3722-g417ea5c02cef7f000e66d1af22b066c2c1cda047

Additionally, it turned out that all call to load_file called exit
explicitly - except for the main file via gfc_init -> gfc_new_file. The
latter also output a file not existing fatal error, such that two errors
where printed. Now exit is called in line with the other users of
load_file.

Finally, when compileing with "nonexisting/file.f90", first a warning that
"nonexisting" does not exist as include path was printed before the file
not found error was printed. Now the directory in which the physical file
is located is added silently, relying on the file-not-found diagnostic for
those.

	PR fortran/55534
gcc/ChangeLog:

	* doc/invoke.texi (-Wno-missing-include-dirs.): Document Fortran
	behavior.

gcc/fortran/ChangeLog:

	* cpp.c (gfc_cpp_register_include_paths, gfc_cpp_post_options):
	Add new bool verbose_missing_dir_warn argument.
	* cpp.h (gfc_cpp_post_options): Update prototype.
	* f95-lang.c (gfc_init): Remove duplicated file-not found diag.
	* gfortran.h (gfc_check_include_dirs): Takes bool
	verbose_missing_dir_warn arg.
	(gfc_new_file): Returns now void.
	* options.c (gfc_post_options): Update to warn for -I and -J,
	only, by default but for all when user requested.
	* scanner.c (gfc_do_check_include_dir):
	(gfc_do_check_include_dirs, gfc_check_include_dirs): Take bool
	verbose warn arg and update to avoid printing the same message
	twice or never.
	(load_file): Fix indent.
	(gfc_new_file): Return void and exit when load_file failed
	as all other load_file users do.

libgfortran/ChangeLog:

	* configure.ac (AM_FCFLAGS): Revert r12-3722 by removing
	-Wno-missing-include-dirs.
	* configure: Regenerate.
    
libgomp/ChangeLog:

	* testsuite/libgomp.fortran/fortran.exp (ALWAYS_CFLAGS): Revert
	r12-3722 by removing -Wno-missing-include-dirs.
	* testsuite/libgomp.oacc-fortran/fortran.exp (ALWAYS_CFLAGS): Likewise.

gcc/testsuite/ChangeLog:

	* gfortran.dg/include_14.f90: Add -J testcase and update dg-output.
	* gfortran.dg/include_15.f90: Likewise.
	* gfortran.dg/include_16.f90: Likewise.
	* gfortran.dg/include_17.f90: Likewise.
	* gfortran.dg/include_18.f90: Likewise.
	* gfortran.dg/include_19.f90: Likewise.

 gcc/doc/invoke.texi                                |  6 +++--
 gcc/fortran/cpp.c                                  |  9 ++++----
 gcc/fortran/cpp.h                                  |  2 +-
 gcc/fortran/f95-lang.c                             |  4 ++--
 gcc/fortran/gfortran.h                             |  4 ++--
 gcc/fortran/options.c                              | 19 +++++++++++----
 gcc/fortran/scanner.c                              | 27 ++++++++++++++--------
 gcc/testsuite/gfortran.dg/include_14.f90           |  7 +++---
 gcc/testsuite/gfortran.dg/include_15.f90           |  7 +++---
 gcc/testsuite/gfortran.dg/include_16.f90           |  2 +-
 gcc/testsuite/gfortran.dg/include_17.f90           |  4 +++-
 gcc/testsuite/gfortran.dg/include_18.f90           |  4 +++-
 gcc/testsuite/gfortran.dg/include_19.f90           |  2 +-
 libgfortran/configure                              |  2 +-
 libgfortran/configure.ac                           |  2 +-
 libgomp/testsuite/libgomp.fortran/fortran.exp      |  3 ---
 libgomp/testsuite/libgomp.oacc-fortran/fortran.exp |  3 ---
 17 files changed, 63 insertions(+), 44 deletions(-)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 4acb94181d2..ba98eab68a5 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -6459,10 +6459,12 @@ int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @};
 
 This warning is enabled by @option{-Wall}.
 
-@item -Wmissing-include-dirs @r{(C, C++, Objective-C and Objective-C++ only)}
+@item -Wmissing-include-dirs @r{(C, C++, Objective-C, Objective-C++ and Fortran only)}
 @opindex Wmissing-include-dirs
 @opindex Wno-missing-include-dirs
-Warn if a user-supplied include directory does not exist.
+Warn if a user-supplied include directory does not exist. This opions is disabled
+by default for C, C++, Objective-C and Objective-C++. For Fortran, it is partially
+enabled by default by warning for -I and -J, only.
 
 @item -Wno-missing-profile
 @opindex Wmissing-profile
diff --git a/gcc/fortran/cpp.c b/gcc/fortran/cpp.c
index 3ff895455e9..e86386c8b17 100644
--- a/gcc/fortran/cpp.c
+++ b/gcc/fortran/cpp.c
@@ -245,11 +245,12 @@ gfc_cpp_temporary_file (void)
 }
 
 static void
-gfc_cpp_register_include_paths (void)
+gfc_cpp_register_include_paths (bool verbose_missing_dir_warn)
 {
   int cxx_stdinc = 0;
   cpp_get_options (cpp_in)->warn_missing_include_dirs
-    = global_options.x_cpp_warn_missing_include_dirs;
+    = (global_options.x_cpp_warn_missing_include_dirs
+       && verbose_missing_dir_warn);
   register_include_chains (cpp_in, gfc_cpp_option.sysroot,
 			   gfc_cpp_option.prefix, gfc_cpp_option.multilib,
 			   gfc_cpp_option.standard_include_paths, cxx_stdinc,
@@ -484,7 +485,7 @@ gfc_cpp_init_cb (void)
 }
 
 void
-gfc_cpp_post_options (void)
+gfc_cpp_post_options (bool verbose_missing_dir_warn)
 {
   /* Any preprocessing-related option without '-cpp' is considered
      an error.  */
@@ -547,7 +548,7 @@ gfc_cpp_post_options (void)
   diagnostic_initialize_input_context (global_dc, nullptr, true);
   gfc_cpp_init_cb ();
 
-  gfc_cpp_register_include_paths ();
+  gfc_cpp_register_include_paths (verbose_missing_dir_warn);
 }
 
 
diff --git a/gcc/fortran/cpp.h b/gcc/fortran/cpp.h
index 5cb7e5a9c34..44644a2a333 100644
--- a/gcc/fortran/cpp.h
+++ b/gcc/fortran/cpp.h
@@ -41,7 +41,7 @@ void gfc_cpp_init_options (unsigned int decoded_options_count,
 
 int gfc_cpp_handle_option(size_t scode, const char *arg, int value);
 
-void gfc_cpp_post_options (void);
+void gfc_cpp_post_options (bool);
 
 bool gfc_cpp_preprocess (const char *source_file);
 
diff --git a/gcc/fortran/f95-lang.c b/gcc/fortran/f95-lang.c
index 026228da09f..58dcaf01d75 100644
--- a/gcc/fortran/f95-lang.c
+++ b/gcc/fortran/f95-lang.c
@@ -259,8 +259,8 @@ gfc_init (void)
 
   gfc_init_1 ();
 
-  if (!gfc_new_file ())
-    fatal_error (input_location, "cannot open input file: %s", gfc_source_file);
+  /* Calls exit in case of a fail. */
+  gfc_new_file ();
 
   if (flag_preprocess_only)
     return false;
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 3c7a8434d07..7ef835b211a 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -3032,7 +3032,7 @@ void gfc_scanner_init_1 (void);
 void gfc_add_include_path (const char *, bool, bool, bool, bool);
 void gfc_add_intrinsic_modules_path (const char *);
 void gfc_release_include_path (void);
-void gfc_check_include_dirs (void);
+void gfc_check_include_dirs (bool);
 FILE *gfc_open_included_file (const char *, bool, bool);
 
 int gfc_at_end (void);
@@ -3064,7 +3064,7 @@ gfc_char_t gfc_peek_char (void);
 char gfc_peek_ascii_char (void);
 void gfc_error_recovery (void);
 void gfc_gobble_whitespace (void);
-bool gfc_new_file (void);
+void gfc_new_file (void);
 const char * gfc_read_orig_filename (const char *, const char **);
 
 extern gfc_source_form gfc_current_form;
diff --git a/gcc/fortran/options.c b/gcc/fortran/options.c
index d789397515a..016b70443ae 100644
--- a/gcc/fortran/options.c
+++ b/gcc/fortran/options.c
@@ -251,14 +251,20 @@ gfc_post_options (const char **pfilename)
 {
   const char *filename = *pfilename, *canon_source_file = NULL;
   char *source_path;
+  bool verbose_missing_dir_warn;
   int i;
 
   /* This needs to be after the commandline has been processed.
      In Fortran, the options is by default enabled, in C/C++
-     by default disabled.  */
+     by default disabled.
+     If not enabled explicitly by the user, only warn for -I
+     and -J, otherwise warn for all include paths.  */
+  verbose_missing_dir_warn
+    = (global_options_set.x_cpp_warn_missing_include_dirs
+       && global_options.x_cpp_warn_missing_include_dirs);
   SET_OPTION_IF_UNSET (&global_options, &global_options_set,
 		       cpp_warn_missing_include_dirs, 1);
-  gfc_check_include_dirs ();
+  gfc_check_include_dirs (verbose_missing_dir_warn);
 
   /* Finalize DEC flags.  */
   post_dec_flags (flag_dec);
@@ -339,10 +345,13 @@ gfc_post_options (const char **pfilename)
       source_path = (char *) alloca (i + 1);
       memcpy (source_path, canon_source_file, i);
       source_path[i] = 0;
-      gfc_add_include_path (source_path, true, true, true, false);
+      /* Only warn if the directory is different from the input file as
+	 if that one is not found, already an error is shown.  */
+      bool warn = gfc_option.flag_preprocessed && gfc_source_file != filename;
+      gfc_add_include_path (source_path, true, true, warn, false);
     }
   else
-    gfc_add_include_path (".", true, true, true, false);
+    gfc_add_include_path (".", true, true, false, false);
 
   if (canon_source_file != gfc_source_file)
     free (CONST_CAST (char *, canon_source_file));
@@ -490,7 +499,7 @@ gfc_post_options (const char **pfilename)
     gfc_fatal_error ("Maximum subrecord length cannot exceed %d",
 		     MAX_SUBRECORD_LENGTH);
 
-  gfc_cpp_post_options ();
+  gfc_cpp_post_options (verbose_missing_dir_warn);
 
   if (gfc_option.allow_std & GFC_STD_F2008)
     lang_hooks.name = "GNU Fortran2008";
diff --git a/gcc/fortran/scanner.c b/gcc/fortran/scanner.c
index 6fe74bd5b8d..52124bd5d36 100644
--- a/gcc/fortran/scanner.c
+++ b/gcc/fortran/scanner.c
@@ -307,9 +307,9 @@ gfc_do_check_include_dir (const char *path, bool warn)
       if (errno != ENOENT)
 	gfc_warning_now (0, "Include directory %qs: %s",
 			 path, xstrerror(errno));
-      else if (warn && !gfc_cpp_enabled ())
+      else if (warn)
 	  gfc_warning_now (OPT_Wmissing_include_dirs,
-			     "Nonexistent include directory %qs", path);
+			   "Nonexistent include directory %qs", path);
       return false;
     }
   else if (!S_ISDIR (st.st_mode))
@@ -323,7 +323,7 @@ gfc_do_check_include_dir (const char *path, bool warn)
 /* In order that -W(no-)missing-include-dirs works, the diagnostic can only be
    run after processing the commandline.  */
 static void
-gfc_do_check_include_dirs (gfc_directorylist **list)
+gfc_do_check_include_dirs (gfc_directorylist **list, bool do_warn)
 {
   gfc_directorylist *prev, *q, *n;
   prev = NULL;
@@ -331,7 +331,7 @@ gfc_do_check_include_dirs (gfc_directorylist **list)
   while (n)
     {
       q = n; n = n->next;
-      if (gfc_do_check_include_dir (q->path, q->warn))
+      if (gfc_do_check_include_dir (q->path, q->warn && do_warn))
 	{
 	  prev = q;
 	  continue;
@@ -346,10 +346,16 @@ gfc_do_check_include_dirs (gfc_directorylist **list)
 }
 
 void
-gfc_check_include_dirs ()
+gfc_check_include_dirs (bool verbose_missing_dir_warn)
 {
-  gfc_do_check_include_dirs (&include_dirs);
-  gfc_do_check_include_dirs (&intrinsic_modules_dirs);
+  /* This is a bit convoluted: If gfc_cpp_enabled () and
+     verbose_missing_dir_warn, the warning is shown by libcpp. Otherwise,
+     it is shown here, still conditional on OPT_Wmissing_include_dirs.  */
+  bool warn = !gfc_cpp_enabled () || !verbose_missing_dir_warn;
+  gfc_do_check_include_dirs (&include_dirs, warn);
+  gfc_do_check_include_dirs (&intrinsic_modules_dirs, verbose_missing_dir_warn);
+  if (gfc_option.module_dir && gfc_cpp_enabled ())
+    gfc_do_check_include_dirs (&include_dirs, true);
 }
 
 /* Adds path to the list pointed to by list.  */
@@ -2771,7 +2777,7 @@ load_file (const char *realfilename, const char *displayedname, bool initial)
    it tries to determine the source form from the filename, defaulting
    to free form.  */
 
-bool
+void
 gfc_new_file (void)
 {
   bool result;
@@ -2789,6 +2795,9 @@ gfc_new_file (void)
   else
     result = load_file (gfc_source_file, NULL, true);
 
+  if (!result)
+    exit (FATAL_EXIT_CODE);
+
   gfc_current_locus.lb = line_head;
   gfc_current_locus.nextc = (line_head == NULL) ? NULL : line_head->line;
 
@@ -2799,8 +2808,6 @@ gfc_new_file (void)
 
   exit (SUCCESS_EXIT_CODE);
 #endif
-
-  return result;
 }
 
 static char *
diff --git a/gcc/testsuite/gfortran.dg/include_14.f90 b/gcc/testsuite/gfortran.dg/include_14.f90
index b306b2c813b..8110e49bf43 100644
--- a/gcc/testsuite/gfortran.dg/include_14.f90
+++ b/gcc/testsuite/gfortran.dg/include_14.f90
@@ -1,5 +1,6 @@
-! { dg-additional-options "-cpp -idirafter /fdaf/ -I bar" }
+! { dg-additional-options "-cpp -idirafter /fdaf/ -I bar -J foo/bar" }
 end
+! default: warn for -I and -J but ignore other options.
+! { dg-warning "Nonexistent include directory 'bar/'" "" { target *-*-* } 0 }
+! { dg-warning "Nonexistent include directory 'foo/bar/'" "" { target *-*-* } 0 }
 
-! { dg-warning "/fdaf/: No such file or directory" "" { target *-*-* } 0 }
-! { dg-warning "bar: No such file or directory" "" { target *-*-* } 0 }
diff --git a/gcc/testsuite/gfortran.dg/include_15.f90 b/gcc/testsuite/gfortran.dg/include_15.f90
index 4944282f931..068dcef5826 100644
--- a/gcc/testsuite/gfortran.dg/include_15.f90
+++ b/gcc/testsuite/gfortran.dg/include_15.f90
@@ -1,5 +1,6 @@
-! { dg-additional-options "-cpp -idirafter /fdaf/ -I bar -Wmissing-include-dirs" }
+! { dg-additional-options "-cpp -idirafter /fdaf/ -I bar -J foo/bar -Wmissing-include-dirs" }
 end
 
-! { dg-warning "/fdaf/: No such file or directory" "" { target *-*-* } 0 }
-! { dg-warning "bar: No such file or directory" "" { target *-*-* } 0 }
+! { dg-warning " /fdaf/: No such file or directory" "" { target *-*-* } 0 }
+! { dg-warning " bar: No such file or directory" "" { target *-*-* } 0 }
+! { dg-warning " foo/bar: No such file or directory" "" { target *-*-* } 0 }
diff --git a/gcc/testsuite/gfortran.dg/include_16.f90 b/gcc/testsuite/gfortran.dg/include_16.f90
index 45794f28e73..65e4c7efdad 100644
--- a/gcc/testsuite/gfortran.dg/include_16.f90
+++ b/gcc/testsuite/gfortran.dg/include_16.f90
@@ -1,2 +1,2 @@
-! { dg-additional-options "-cpp -idirafter /fdaf/ -I bar -Wno-missing-include-dirs" }
+! { dg-additional-options "-cpp -idirafter /fdaf/ -I bar -J foo/bar -Wno-missing-include-dirs" }
 end
diff --git a/gcc/testsuite/gfortran.dg/include_17.f90 b/gcc/testsuite/gfortran.dg/include_17.f90
index 0ed5c86d323..06677590be3 100644
--- a/gcc/testsuite/gfortran.dg/include_17.f90
+++ b/gcc/testsuite/gfortran.dg/include_17.f90
@@ -1,4 +1,6 @@
 ! { dg-do compile }
-! { dg-options "-I foo-bar -Wno-missing-include-dirs" }
+! { dg-options "-I foo-bar -J foo/bar" }
 end 
+! { dg-warning "Nonexistent include directory 'foo-bar/'" "" { target *-*-* } 0 }
+! { dg-warning "Nonexistent include directory 'foo/bar/'" "" { target *-*-* } 0 }
 
diff --git a/gcc/testsuite/gfortran.dg/include_18.f90 b/gcc/testsuite/gfortran.dg/include_18.f90
index ca69df382fe..b74a585bf1b 100644
--- a/gcc/testsuite/gfortran.dg/include_18.f90
+++ b/gcc/testsuite/gfortran.dg/include_18.f90
@@ -1,3 +1,5 @@
 ! { dg-do compile }
-! { dg-options "-I nothere -Wno-missing-include-dirs" }
+! { dg-options "-I nothere -J neither/here -Wmissing-include-dirs" }
 end 
+! { dg-warning "Nonexistent include directory 'nothere/'" "" { target *-*-* } 0 }
+! { dg-warning "Nonexistent include directory 'neither/here/'" "" { target *-*-* } 0 }
diff --git a/gcc/testsuite/gfortran.dg/include_19.f90 b/gcc/testsuite/gfortran.dg/include_19.f90
index 2a068174b7e..74049295281 100644
--- a/gcc/testsuite/gfortran.dg/include_19.f90
+++ b/gcc/testsuite/gfortran.dg/include_19.f90
@@ -1,4 +1,4 @@
 ! { dg-do compile }
-! { dg-options "-J foobar/foo -Wno-missing-include-dirs" }
+! { dg-options "-I nothere -J foobar/foo -Wno-missing-include-dirs" }
 program main
 end program main
diff --git a/libgfortran/configure b/libgfortran/configure
index 350159aa4fe..4810b9b032e 100755
--- a/libgfortran/configure
+++ b/libgfortran/configure
@@ -5985,7 +5985,7 @@ fi
 
 # Add -Wall -fno-repack-arrays -fno-underscoring if we are using GCC.
 if test "x$GCC" = "xyes"; then
-  AM_FCFLAGS="-I . -Wall -Werror -fimplicit-none -fno-repack-arrays -fno-underscoring -Wno-missing-include-dirs"
+  AM_FCFLAGS="-I . -Wall -Werror -fimplicit-none -fno-repack-arrays -fno-underscoring"
   ## We like to use C11 and C99 routines when available.  This makes
   ## sure that
   ## __STDC_VERSION__ is set such that libc includes make them available.
diff --git a/libgfortran/configure.ac b/libgfortran/configure.ac
index a3550b4e5d0..a77509801e6 100644
--- a/libgfortran/configure.ac
+++ b/libgfortran/configure.ac
@@ -146,7 +146,7 @@ AM_PROG_CC_C_O
 
 # Add -Wall -fno-repack-arrays -fno-underscoring if we are using GCC.
 if test "x$GCC" = "xyes"; then
-  AM_FCFLAGS="-I . -Wall -Werror -fimplicit-none -fno-repack-arrays -fno-underscoring -Wno-missing-include-dirs"
+  AM_FCFLAGS="-I . -Wall -Werror -fimplicit-none -fno-repack-arrays -fno-underscoring"
   ## We like to use C11 and C99 routines when available.  This makes
   ## sure that
   ## __STDC_VERSION__ is set such that libc includes make them available.
diff --git a/libgomp/testsuite/libgomp.fortran/fortran.exp b/libgomp/testsuite/libgomp.fortran/fortran.exp
index 912dd2a743e..eb701311b6a 100644
--- a/libgomp/testsuite/libgomp.fortran/fortran.exp
+++ b/libgomp/testsuite/libgomp.fortran/fortran.exp
@@ -20,9 +20,6 @@ dg-init
 
 # Turn on OpenMP.
 lappend ALWAYS_CFLAGS "additional_flags=-fopenmp"
-# Silence warnings due to explicitly passed but nonexisting
-# -isystem <instdir>/target>/{sys-,}include (gfortran warns by default)
-lappend ALWAYS_CFLAGS "additional_flags=-Wno-missing-include-dirs"
 
 if { $blddir != "" } {
     set lang_source_re {^.*\.[fF](|90|95|03|08)$}
diff --git a/libgomp/testsuite/libgomp.oacc-fortran/fortran.exp b/libgomp/testsuite/libgomp.oacc-fortran/fortran.exp
index 22e91eca256..7365b320668 100644
--- a/libgomp/testsuite/libgomp.oacc-fortran/fortran.exp
+++ b/libgomp/testsuite/libgomp.oacc-fortran/fortran.exp
@@ -22,9 +22,6 @@ dg-init
 
 # Turn on OpenACC.
 lappend ALWAYS_CFLAGS "additional_flags=-fopenacc"
-# Silence warnings due to explicitly passed but nonexisting
-# -isystem <instdir>/target>/{sys-,}include (gfortran warns by default)
-lappend ALWAYS_CFLAGS "additional_flags=-Wno-missing-include-dirs"
 
 if { $blddir != "" } {
     set lang_source_re {^.*\.[fF](|90|95|03|08)$}
