Filter out C, C++ build flags from Fortran build flags (#2177253)

And pave the way for future front-end-specific compiler flags.

buildflags.md

@@ -36,9 +36,7 @@ Individual build flags are also available through RPM macros:
 * `%{build_cxx}` for the command name of the C++ compiler.
 * `%{build_cpp}` for the command name of the C-compatible preprocessor.
 * `%{build_cflags}` for the C compiler flags (also known as the
-  `CFLAGS` variable). Also historically available as `%{optflags}`.
+  `CFLAGS` variable).
-  Furthermore, at the start of the `%build` section, the environment
-  variable `RPM_OPT_FLAGS` is set to this value.
 * `%{build_cxxflags}` for the C++ compiler flags (usually assigned to
   the `CXXFLAGS` shell variable).
 * `%{build_fflags}` for `FFLAGS` (the Fortran compiler flags, also
@@ -50,6 +48,13 @@ Individual build flags are also available through RPM macros:
   driver. At the start of the `%build` section, the environment
   variable `RPM_LD_FLAGS` is set to this value.
 
+The C and C++ compiler flags are historically available as the
+`%{optflags}` macro.  These flags may not contain flags that work with
+certain languagues or compiler front ends, so the language-specific
+`%build_*` are more precise.  At the start of the `%build` section,
+the environment variable `RPM_OPT_FLAGS` is set to the `%{optflags}`
+value; similar limitations apply.
+
 The variable `LT_SYS_LIBRARY_PATH` is defined here to prevent the `libtool`
 script (v2.4.6+) from hardcoding `%_libdir` into the binaries' `RPATH`.
 
@@ -402,6 +407,9 @@ The general (architecture-independent) build flags are:
   compilation performance.  (This does not affect code generation.)
 * `-Wall`: Turn on various GCC warnings.
   See the [GCC manual](https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wall).
+* `-Wno-complain-wrong-lang`: Do not warn about front end mismatches
+  (e.g, using `-Werror=format-security` with Fortran).  Only included
+  in `%optflags`, and not the front-end-specific `%build_*` macros.
 * `-Werror=format-security`: Turn on format string warnings and treat
   them as errors.
   See the [GCC manual](https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wformat-security).

macros

@@ -57,14 +57,14 @@
 # C compiler flags.  This is traditionally called CFLAGS in makefiles.
 # Historically also available as %%{optflags}, and %%build sets the
 # environment variable RPM_OPT_FLAGS to this value.
-%build_cflags %{optflags} %{?_distro_extra_cflags}
+%build_cflags %{__build_flags_lang_c} %{?_distro_extra_cflags}
 
 # C++ compiler flags.  This is traditionally called CXXFLAGS in makefiles.
-%build_cxxflags %{optflags} %{?_distro_extra_cxxflags}
+%build_cxxflags %{__build_flags_lang_cxx} %{?_distro_extra_cxxflags}
 
 # Fortran compiler flags.  Makefiles use both FFLAGS and FCFLAGS as
 # the corresponding variable names.
-%build_fflags %{optflags} -I%{_fmoddir} %{?_distro_extra_fflags}
+%build_fflags %{__build_flags_common} -I%{_fmoddir} %{?_distro_extra_fflags}
 
 # Vala compiler flags. This is used to set VALAFLAGS.
 %build_valaflags -g
@@ -308,6 +308,12 @@ print(result)
 # Use Zstandard compression for binary payloads
 %_binary_payload w19.zstdio
 
+#==============================================================================
+# --- Compiler flags control.
+#
+# Please consult buildflags.md for parts that can be configured
+# from RPM spec files.
+
 %_hardening_gcc_cflags   -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
 %_hardening_clang_cflags --config /usr/lib/rpm/redhat/redhat-hardened-clang.cfg
 %_hardening_cflags	 %{expand:%%{_hardening_%{toolchain}_cflags}} -fstack-protector-strong
@@ -383,7 +389,7 @@ print(result)
 %_build_id_flags	-Wl,--build-id=sha1
 
 %_general_options       -O2 %{?_lto_cflags} -fexceptions -g -grecord-gcc-switches -pipe
-%_warning_options       -Wall -Werror=format-security
+%_warning_options       -Wall%[%__build_for_lang_any ? " -Wno-complain-wrong-lang" : ""]%[%__build_for_lang_c + %__build_for_lang_cxx ? " -Werror=format-security" : ""]
 %_preprocessor_defines  %{_fortify_level_flags} -Wp,-D_GLIBCXX_ASSERTIONS
 
 # Common variables are no longer generated by default by gcc and clang
@@ -392,6 +398,21 @@ print(result)
 
 %__global_compiler_flags %{_general_options} %{_warning_options} %{_preprocessor_defines} %{_hardened_cflags} %{_annotation_cflags} %{_legacy_options}
 
+# Internal macros. Do not use directly.  These variables can be rebound
+# to suppress certain frontend-specific compiler flags (or in the case
+# of __build_for_lang_any, frontend-agnostic flags).  Dynamic scoping
+# and shadowing redefinitions are used for the __build_for_* variables
+# to remain largely compatible with existing spec files that have
+# hard-coded assumptions which macros assume which other macros.
+# Note: Using short-circuit evaluation with || in __build_for_* conditionals
+# may result in unused-macro warnings from RPM.
+%__build_for_lang_c 1
+%__build_for_lang_cxx 1
+%__build_for_lang_any 1
+%__build_flags_common() %{expand:%define __build_for_lang_c 0}%{expand:%define __build_for_lang_cxx 0}%{expand:%define __build_for_lang_any 0}%{optflags}
+%__build_flags_lang_c() %{expand:%define __build_for_lang_cxx 0}%{expand:%define __build_for_lang_any 0}%{optflags}
+%__build_flags_lang_cxx() %{expand:%define __build_for_lang_c 0}%{expand:%define __build_for_lang_any 0}%{optflags}
+
 # Automatically trim changelog entries after 2 years
 %_changelog_trimage	%{expr:2*365*24*60*60}
 

redhat-rpm-config.spec

@@ -4,7 +4,7 @@
 # 2) When making changes, increment the version (in baserelease) by 1.
 #    rpmdev-bumpspec and other tools update the macro below, which is used
 #    in Version: to get the desired effect.
-%global baserelease 258
+%global baserelease 259
 
 Summary: Red Hat specific rpm configuration files
 Name: redhat-rpm-config
@@ -254,6 +254,9 @@ install -p -m 644 -t %{buildroot}%{_rpmluadir}/fedora/srpm forge.lua
 %doc buildflags.md
 
 %changelog
+* Wed Jul  5 2023 Florian Weimer <fweimer@redhat.com> - 259-1
+- Filter out C, C++ build flags from Fortran build flags (#2177253)
+
 * Wed Jul  5 2023 Florian Weimer <fweimer@redhat.com> - 258-1
 - Enable PIC mode for assembler files (#2167430)