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* [Patch] OpenMP: Document ompx warnings + add Fortran omx warning [PR106670]
@ 2022-08-29  9:24 Tobias Burnus
  2022-08-29  9:24 ` Tobias Burnus
  2022-09-08 15:47 ` Jakub Jelinek
  0 siblings, 2 replies; 3+ messages in thread
From: Tobias Burnus @ 2022-08-29  9:24 UTC (permalink / raw)
  To: gcc-patches, fortran, Jakub Jelinek

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(Patch + RFC.)

OpenMP 5.2 has 'ompx' and (for fixed source form Fortran) 'omx'
as sentinel to provide a defined namespace for vendor extensions.

The behavior when encountering an unknown directive with ompx/omp sentinel
(or an unknown clause with ompx_ prefix) is implementation defined. For unknown
clauses there will be always an error in GCC.
For sentinels, GCC compiles the code and ignores the directive.
From the user perspective, either silently ignoring the directive or
showing a warning or showing an erroring is best - depending on the semantic
of that vendor extension. As the semantic is not known, providing a means
to warn makes most sense.

For warning, we can either show a
- specific message for ompx/omx - or a
- generic message
And we can either use some existing generic flag (unknown pragmas,
attributes, suprising behavior etc.), depending on language and source
language (C, C++, Fortran fixed/free)- or add & use a specific -W flag.

The attached patch just documents the existing warning behavior, which
is quite diverse + adds testcases for them. As fixed-form Fortran had no
warning, a new warning with a specific message was added.
(Cf. testcases in the patch for what's shown as message.)

OK for mainline - or other ideas how to handle this topic best?

Tobias


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OpenMP: Document ompx warnings + add Fortran omx warning [PR106670]

omp/ompx sentinels are for vendor extensions; as they might be required for
the correctness of the program, a warning should be printable. This patch
documents in the OpenMP 5.2 table the existing warnings, including the new
warning for for fixed source form Fortran.

	PR fortran/106670

gcc/fortran/ChangeLog:

	* scanner.cc (skip_fixed_omp_sentinel): Add -Wsurprising warning
	for 'omx' sentinels with -fopenmp.
	* invoke.texi (-Wsurprising): Document additional warning case.

libgomp/ChangeLog:

	* libgomp.texi (OpenMP 5.2): Add comment to ompx/omx entry.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/ompx-1.c: New test.
	* c-c++-common/gomp/ompx-2.c: New test.
	* g++.dg/gomp/ompx-attrs-1.C: New test.
	* gfortran.dg/gomp/ompx-1.f90: New test.
	* gfortran.dg/gomp/omx-1.f: New test.
	* gfortran.dg/gomp/omx-2.f: New test.

 gcc/fortran/invoke.texi                   | 5 +++++
 gcc/fortran/scanner.cc                    | 8 ++++++--
 gcc/testsuite/c-c++-common/gomp/ompx-1.c  | 4 ++++
 gcc/testsuite/c-c++-common/gomp/ompx-2.c  | 5 +++++
 gcc/testsuite/g++.dg/gomp/ompx-attrs-1.C  | 7 +++++++
 gcc/testsuite/gfortran.dg/gomp/ompx-1.f90 | 2 ++
 gcc/testsuite/gfortran.dg/gomp/omx-1.f    | 7 +++++++
 gcc/testsuite/gfortran.dg/gomp/omx-2.f    | 9 +++++++++
 libgomp/libgomp.texi                      | 8 +++++++-
 9 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi
index 4d1e0d6b513..58502d38ac8 100644
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -1092,6 +1092,11 @@ The type of a function result is declared more than once with the same type.  If
 
 @item
 A @code{CHARACTER} variable is declared with negative length.
+
+@item
+With @option{-fopenmp}, for fixed-form source code, when an @code{omx}
+vendor-extension sentinel is encountered. (The equivalent @code{ompx},
+used in free-form source code, is diagnosed by default.)
 @end itemize
 
 @item -Wtabs
diff --git a/gcc/fortran/scanner.cc b/gcc/fortran/scanner.cc
index 2dff2514700..fa1d9cba394 100644
--- a/gcc/fortran/scanner.cc
+++ b/gcc/fortran/scanner.cc
@@ -982,8 +982,9 @@ static bool
 skip_fixed_omp_sentinel (locus *start)
 {
   gfc_char_t c;
-  if (((c = next_char ()) == 'm' || c == 'M')
-      && ((c = next_char ()) == 'p' || c == 'P'))
+  if ((c = next_char ()) != 'm' && c != 'M')
+    return false;
+  if ((c = next_char ()) == 'p' || c == 'P')
     {
       c = next_char ();
       if (c != '\n'
@@ -1005,6 +1006,9 @@ skip_fixed_omp_sentinel (locus *start)
 	    }
 	}
     }
+  else if (UNLIKELY (c == 'x' || c == 'X'))
+    gfc_warning_now (OPT_Wsurprising,
+		     "Ignoring '!$omx' vendor-extension sentinel at %C");
   return false;
 }
 
diff --git a/gcc/testsuite/c-c++-common/gomp/ompx-1.c b/gcc/testsuite/c-c++-common/gomp/ompx-1.c
new file mode 100644
index 00000000000..9758d0f0cae
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/gomp/ompx-1.c
@@ -0,0 +1,4 @@
+void f(void)
+{
+  #pragma ompx some_vendor_extension
+}
diff --git a/gcc/testsuite/c-c++-common/gomp/ompx-2.c b/gcc/testsuite/c-c++-common/gomp/ompx-2.c
new file mode 100644
index 00000000000..4b66b0e2b1c
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/gomp/ompx-2.c
@@ -0,0 +1,5 @@
+/* { dg-additional-options "-Wunknown-pragmas" } */
+void f(void)
+{
+  #pragma ompx some_vendor_extension  /* { dg-warning "-:ignoring '#pragma ompx some_vendor_extension'" } */
+}
diff --git a/gcc/testsuite/g++.dg/gomp/ompx-attrs-1.C b/gcc/testsuite/g++.dg/gomp/ompx-attrs-1.C
new file mode 100644
index 00000000000..2e9fc0b591f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/gomp/ompx-attrs-1.C
@@ -0,0 +1,7 @@
+// { dg-do compile { target c++11 } }
+
+void
+foo ()
+{
+  [[ompx::directive(some_vendor_extension)]];  /* { dg-warning "attributes at the beginning of statement are ignored" } */
+}
diff --git a/gcc/testsuite/gfortran.dg/gomp/ompx-1.f90 b/gcc/testsuite/gfortran.dg/gomp/ompx-1.f90
new file mode 100644
index 00000000000..e5dc6520fd4
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/ompx-1.f90
@@ -0,0 +1,2 @@
+!$ompx foo  ! { dg-warning "!.OMP at .1. starts a commented line as it neither is followed by a space nor is a continuation line" }
+end
diff --git a/gcc/testsuite/gfortran.dg/gomp/omx-1.f b/gcc/testsuite/gfortran.dg/gomp/omx-1.f
new file mode 100644
index 00000000000..4febf8908bf
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/omx-1.f
@@ -0,0 +1,7 @@
+!$omx foo
+!$OMX foo
+c$oMx foo
+c$OMx foo
+*$oMx foo
+*$OMx foo
+      end
diff --git a/gcc/testsuite/gfortran.dg/gomp/omx-2.f b/gcc/testsuite/gfortran.dg/gomp/omx-2.f
new file mode 100644
index 00000000000..3c107d98367
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/omx-2.f
@@ -0,0 +1,9 @@
+! { dg-additional-options "-Wsurprising" }
+
+!$omx foo  ! { dg-warning "Ignoring '!.omx' vendor-extension sentinel" }
+!$OMX foo  ! { dg-warning "Ignoring '!.omx' vendor-extension sentinel" }
+c$oMx foo  ! { dg-warning "Ignoring '!.omx' vendor-extension sentinel" }
+c$OMx foo  ! { dg-warning "Ignoring '!.omx' vendor-extension sentinel" }
+*$oMx foo  ! { dg-warning "Ignoring '!.omx' vendor-extension sentinel" }
+*$OMx foo  ! { dg-warning "Ignoring '!.omx' vendor-extension sentinel" }
+      end
diff --git a/libgomp/libgomp.texi b/libgomp/libgomp.texi
index 0f2998cf8f1..6298de8254c 100644
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -359,7 +359,13 @@ to address of matching mapped list item per 5.1, Sect. 2.21.7.2 @tab N @tab
 @item @code{omp_in_explicit_task} routine and @emph{implicit-task-var} ICV
       @tab N @tab
 @item @code{omp}/@code{ompx}/@code{omx} sentinels and @code{omp_}/@code{ompx_}
-      namespaces @tab N/A @tab
+      namespaces @tab N/A
+      @tab warning for @code{omp/ompx} sentinels@footnote{@code{omp/ompx}
+      sentinels as C/C++ pragma and C++ attributes are warned for with
+      @code{-Wunknown-pragmas} (implied by @code{-Wall}) and @code{-Wattributes}
+      (by default), respectively; for Fortran free-source code, the there is a
+      warning by default and for fixed-source code with @code{-Wsurprising}
+      (enabled by @code{-Wall})}
 @item Clauses on @code{end} directive can be on directive @tab N @tab
 @item Deprecation of no-argument @code{destroy} clause on @code{depobj}
       @tab N @tab

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2022-08-29  9:24 [Patch] OpenMP: Document ompx warnings + add Fortran omx warning [PR106670] Tobias Burnus
2022-08-29  9:24 ` Tobias Burnus
2022-09-08 15:47 ` Jakub Jelinek

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