[flang] [llvm] [flang/flang-rt] Implement PERROR intrinsic form GNU Extension (PR #132406)

[Jean-Didier PAILLEUX via llvm-commits]

https://github.com/JDPailleux created https://github.com/llvm/llvm-project/pull/132406

Add the implementation of the `PERROR(STRING) ` intrinsic from the GNU Extension to prints on the stderr a newline-terminated error message corresponding to the last system error prefixed by `STRING`.
(https://gcc.gnu.org/onlinedocs/gfortran/PERROR.html)

>From 5df86daadc21fdf88643f0907534d570cdacb05c Mon Sep 17 00:00:00 2001
From: Jean-Didier Pailleux <jean-didier.pailleux at sipearl.com>
Date: Thu, 20 Mar 2025 11:33:18 +0100
Subject: [PATCH] [flang/flang-rt] Implement PERROR intrinsic form GNU
 Extension

---
 flang-rt/lib/runtime/extensions.cpp      |  4 ++++
 flang/docs/Intrinsics.md                 | 12 ++++++++++++
 flang/include/flang/Runtime/extensions.h |  3 +++
 flang/test/Lower/Intrinsics/perror.f90   | 14 ++++++++++++++
 4 files changed, 33 insertions(+)
 create mode 100644 flang/test/Lower/Intrinsics/perror.f90

diff --git a/flang-rt/lib/runtime/extensions.cpp b/flang-rt/lib/runtime/extensions.cpp
index 75195c33a6c21..c2d47a13d52dd 100644
--- a/flang-rt/lib/runtime/extensions.cpp
+++ b/flang-rt/lib/runtime/extensions.cpp
@@ -17,6 +17,7 @@
 #include "flang/Runtime/entry-names.h"
 #include "flang/Runtime/io-api.h"
 #include <chrono>
+#include <cstdio>
 #include <cstring>
 #include <ctime>
 #include <signal.h>
@@ -262,5 +263,8 @@ int RTNAME(Chdir)(const char *name) {
 
 int FORTRAN_PROCEDURE_NAME(ierrno)() { return errno; }
 
+// PERROR(STRING)
+void FORTRAN_PROCEDURE_NAME(perror)(const char *str) { perror(str); }
+
 } // namespace Fortran::runtime
 } // extern "C"
diff --git a/flang/docs/Intrinsics.md b/flang/docs/Intrinsics.md
index 5b671d1b2c740..2b5c3bc2fd089 100644
--- a/flang/docs/Intrinsics.md
+++ b/flang/docs/Intrinsics.md
@@ -1106,3 +1106,15 @@ end program chdir_func
 - **Standard:** GNU extension
 - **Class:** function
 - **Syntax:** `RESULT = IERRNO()`
+
+### Non-Standard Intrinsics: PERROR
+
+#### Description
+`PERROR(STRING)` prints (on the C stderr stream) a newline-terminated error message corresponding to the last system error.
+This is prefixed by `STRING`, a colon and a space.
+
+#### Usage and Info
+
+- **Standard:** GNU extension
+- **Class:** subroutine
+- **Syntax:** `CALL PERROR(STRING)`
diff --git a/flang/include/flang/Runtime/extensions.h b/flang/include/flang/Runtime/extensions.h
index 133194dea87cf..b218b9b97ce10 100644
--- a/flang/include/flang/Runtime/extensions.h
+++ b/flang/include/flang/Runtime/extensions.h
@@ -75,5 +75,8 @@ int RTNAME(Chdir)(const char *name);
 // GNU extension function IERRNO()
 int FORTRAN_PROCEDURE_NAME(ierrno)();
 
+// GNU extension subroutine PERROR(STRING)
+void FORTRAN_PROCEDURE_NAME(perror)(const char *str);
+
 } // extern "C"
 #endif // FORTRAN_RUNTIME_EXTENSIONS_H_
diff --git a/flang/test/Lower/Intrinsics/perror.f90 b/flang/test/Lower/Intrinsics/perror.f90
new file mode 100644
index 0000000000000..e42c109f6491c
--- /dev/null
+++ b/flang/test/Lower/Intrinsics/perror.f90
@@ -0,0 +1,14 @@
+! RUN: bbc -emit-fir %s -o - | FileCheck --check-prefixes=CHECK %s
+! RUN: %flang_fc1 -emit-fir %s -o - | FileCheck --check-prefixes=CHECK %s
+
+! CHECK-LABEL: func @_QPtest_perror(
+subroutine test_perror()
+  character(len=10) :: string
+  call perror(string)
+  ! CHECK: %[[C10:.*]] = arith.constant 10 : index
+  ! CHECK: %[[VAL_0:.*]] = fir.alloca !fir.char<1,10> {bindc_name = "string", uniq_name = "_QFtest_perrorEstring"}
+  ! CHECK: %[[VAL_1:.*]] = fir.declare %[[VAL_0]] typeparams %[[C10]] {uniq_name = "_QFtest_perrorEstring"} : (!fir.ref<!fir.char<1,10>>, index) -> !fir.ref<!fir.char<1,10>>
+  ! CHECK: %[[VAL_2:.*]] = fir.emboxchar %[[VAL_1]], %[[C10]] : (!fir.ref<!fir.char<1,10>>, index) -> !fir.boxchar<1>
+  ! CHECK: fir.call @_QPperror(%[[VAL_2]]) fastmath<contract> : (!fir.boxchar<1>) -> () 
+  ! CHECK: return
+end subroutine test_perror