cmake/0008-FortranCInterface-Fix-compatibility-with-GCC-gfortra.patch

From 6a0ce19ce1cb594cdec19bacc9fc7a38156e38da Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Esser?= <besser82@fedoraproject.org>
Date: Wed, 19 Jan 2022 17:26:14 +0100
Subject: [PATCH] FortranCInterface: Fix compatibility with GCC gfortran 12 LTO
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Since version 12.0 the GCC Fortran compiler has implemented "WG5/N1942",
which causes, if link-time opmization is enabled, obfuscation of hard-coded
string values in the compiler objects and its resulting ELF-binaries.

This causes the CMake-internal detection of the mangling scheme for the
naming of subroutines to fail.  Thus we must ensure to have any link-time
optimization features to be disabled on the executable file we perform the
detection on.

The static libraries, however, must be build with LTO and non-LTO objects,
as that will ensure the verify step will operate on IPO objects, if building
those is requested by the system compiler flags.

Fixes: #23123

Signed-off-by: Björn Esser <besser82@fedoraproject.org>
---
 Modules/FortranCInterface/CMakeLists.txt | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/Modules/FortranCInterface/CMakeLists.txt b/Modules/FortranCInterface/CMakeLists.txt
index 13e4498ad9..ce0bc10c8e 100644
--- a/Modules/FortranCInterface/CMakeLists.txt
+++ b/Modules/FortranCInterface/CMakeLists.txt
@@ -102,6 +102,19 @@ set_property(TARGET symbols PROPERTY POSITION_INDEPENDENT_CODE 1)
 add_executable(FortranCInterface main.F call_sub.f ${call_mod})
 target_link_libraries(FortranCInterface PUBLIC symbols)
 
+# If IPO is enabled here, GCC gfortran >= 12.0 will obfuscate
+# the strings of the return values in the compiled executable,
+# which we use to regex match against later.
+# The static libraries must be build with IPO and non-IPO objects,
+# as that will ensure the verify step will operate on IPO objects,
+# if requested by the system compiler flags.
+if(CMAKE_Fortran_COMPILER_ID STREQUAL "GNU" AND
+  CMAKE_Fortran_COMPILER_VERSION VERSION_GREATER_EQUAL 12)
+  target_compile_options(FortranCInterface PRIVATE "-fno-lto")
+  target_compile_options(myfort PRIVATE "-flto=auto" "-ffat-lto-objects")
+  target_compile_options(symbols PRIVATE "-flto=auto" "-ffat-lto-objects")
+endif()
+
 file(GENERATE OUTPUT exe-$<CONFIG>.cmake CONTENT [[
 set(FortranCInterface_EXE "$<TARGET_FILE:FortranCInterface>")
 ]])
-- 
2.34.1