Browse Source
Before this patch, I don't think it was possible to change (say)
CFLAGS as part of running the make command. Nor did setting them when
running configure do anything. Getting this right is a little fiddly:
for example, see Automake's approach at [1] ("AM_CFLAGS" and friends).
This patch adds an "mcppbs-" prefix, and sets things up properly for
CFLAGS, CPPFLAGS, CXXFLAGS and LDFLAGS. Note that the bulk of the
patch is either the auto-generated configure script or the ax_*.m4
files vendored in from the autoconf archive (needed to handle
--export-dynamic correctly without trashing settings from the user
running configure).
What's supposed to happen is as follows:
- Base compilation flags that should apply to everything (standard
optimisation flags, warning flags etc.) are defined in
Makefile.in.
- When the user runs configure, they can set compilation flags on
the command line. These end up as environment variables in the
shell script.
- Compilation flags that can only be decided when we run
configure (this is currently just whether we support
-Wl,--export-dynamic) are appended to the configure-time LDFLAGS
environment variable.
- At the end of the configure script, these environment variables
are spliced into Makefile.in to fill out the corresponding
@<varname>@ entries.
- When running make, the user might again override compilation
flags. These will get appended to the flags found so far.
As a concrete example:
mkdir build
cd build
../configure CXXFLAGS='-O3'
make CXXFLAGS='-O0'
will result in c++ compile commands that look like this:
g++ -MMD -MP \
-DPREFIX=\"/usr/local\" -Wall -Wno-unused -g -O2 -std=c++11 \
-O3 \
-O0 \
-I. -I.. -I../fesvr -I../riscv -I../dummy_rocc -I../softfloat \
-I../spike_main -fPIC -c ../fesvr/elfloader.cc
(I've added some newlines to wrap the long line).
Note that we have the base flags from Makefile.in (called
$(default-CXXFLAGS) there) first. Then we have the -O3 from the
configure command. Finally we have the -O0 from the Make command line.
And I can finally run "make CXXFLAGS='-O0 -g3'". Phew!
[1] https://www.gnu.org/software/automake/manual/html_node/Flag-Variables-Ordering.html
pull/406/head
Rupert Swarbrick
6 years ago
6 changed files with 325 additions and 24 deletions
@ -0,0 +1,50 @@ |
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# =========================================================================== |
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# https://www.gnu.org/software/autoconf-archive/ax_append_flag.html |
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# =========================================================================== |
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# |
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# SYNOPSIS |
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# |
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# AX_APPEND_FLAG(FLAG, [FLAGS-VARIABLE]) |
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# |
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# DESCRIPTION |
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# |
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# FLAG is appended to the FLAGS-VARIABLE shell variable, with a space |
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# added in between. |
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# |
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# If FLAGS-VARIABLE is not specified, the current language's flags (e.g. |
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# CFLAGS) is used. FLAGS-VARIABLE is not changed if it already contains |
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# FLAG. If FLAGS-VARIABLE is unset in the shell, it is set to exactly |
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# FLAG. |
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# |
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# NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. |
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# |
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# LICENSE |
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# |
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# Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de> |
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# Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com> |
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# |
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# Copying and distribution of this file, with or without modification, are |
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# permitted in any medium without royalty provided the copyright notice |
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# and this notice are preserved. This file is offered as-is, without any |
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# warranty. |
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|
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#serial 8 |
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|
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AC_DEFUN([AX_APPEND_FLAG], |
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[dnl |
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AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_SET_IF |
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AS_VAR_PUSHDEF([FLAGS], [m4_default($2,_AC_LANG_PREFIX[FLAGS])]) |
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AS_VAR_SET_IF(FLAGS,[ |
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AS_CASE([" AS_VAR_GET(FLAGS) "], |
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[*" $1 "*], [AC_RUN_LOG([: FLAGS already contains $1])], |
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[ |
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AS_VAR_APPEND(FLAGS,[" $1"]) |
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AC_RUN_LOG([: FLAGS="$FLAGS"]) |
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]) |
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], |
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[ |
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AS_VAR_SET(FLAGS,[$1]) |
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AC_RUN_LOG([: FLAGS="$FLAGS"]) |
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]) |
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AS_VAR_POPDEF([FLAGS])dnl |
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])dnl AX_APPEND_FLAG |
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# =========================================================================== |
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# https://www.gnu.org/software/autoconf-archive/ax_append_link_flags.html |
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# =========================================================================== |
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# |
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# SYNOPSIS |
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# |
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# AX_APPEND_LINK_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS], [INPUT]) |
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# |
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# DESCRIPTION |
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# |
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# For every FLAG1, FLAG2 it is checked whether the linker works with the |
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# flag. If it does, the flag is added FLAGS-VARIABLE |
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# |
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# If FLAGS-VARIABLE is not specified, the linker's flags (LDFLAGS) is |
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# used. During the check the flag is always added to the linker's flags. |
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# |
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# If EXTRA-FLAGS is defined, it is added to the linker's default flags |
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# when the check is done. The check is thus made with the flags: "LDFLAGS |
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# EXTRA-FLAGS FLAG". This can for example be used to force the linker to |
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# issue an error when a bad flag is given. |
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# |
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# INPUT gives an alternative input source to AC_COMPILE_IFELSE. |
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# |
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# NOTE: This macro depends on the AX_APPEND_FLAG and AX_CHECK_LINK_FLAG. |
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# Please keep this macro in sync with AX_APPEND_COMPILE_FLAGS. |
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# |
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# LICENSE |
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# |
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# Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com> |
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# |
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# Copying and distribution of this file, with or without modification, are |
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# permitted in any medium without royalty provided the copyright notice |
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# and this notice are preserved. This file is offered as-is, without any |
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# warranty. |
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|
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#serial 7 |
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|
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AC_DEFUN([AX_APPEND_LINK_FLAGS], |
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[AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG]) |
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AX_REQUIRE_DEFINED([AX_APPEND_FLAG]) |
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for flag in $1; do |
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AX_CHECK_LINK_FLAG([$flag], [AX_APPEND_FLAG([$flag], [m4_default([$2], [LDFLAGS])])], [], [$3], [$4]) |
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done |
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])dnl AX_APPEND_LINK_FLAGS |
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@ -0,0 +1,37 @@ |
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# =========================================================================== |
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# https://www.gnu.org/software/autoconf-archive/ax_require_defined.html |
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# =========================================================================== |
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# |
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# SYNOPSIS |
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# |
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# AX_REQUIRE_DEFINED(MACRO) |
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# |
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# DESCRIPTION |
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# |
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# AX_REQUIRE_DEFINED is a simple helper for making sure other macros have |
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# been defined and thus are available for use. This avoids random issues |
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# where a macro isn't expanded. Instead the configure script emits a |
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# non-fatal: |
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# |
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# ./configure: line 1673: AX_CFLAGS_WARN_ALL: command not found |
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# |
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# It's like AC_REQUIRE except it doesn't expand the required macro. |
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# |
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# Here's an example: |
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# |
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# AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG]) |
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# |
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# LICENSE |
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# |
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# Copyright (c) 2014 Mike Frysinger <vapier@gentoo.org> |
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# |
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# Copying and distribution of this file, with or without modification, are |
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# permitted in any medium without royalty provided the copyright notice |
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# and this notice are preserved. This file is offered as-is, without any |
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# warranty. |
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|
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#serial 2 |
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|
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AC_DEFUN([AX_REQUIRE_DEFINED], [dnl |
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m4_ifndef([$1], [m4_fatal([macro ]$1[ is not defined; is a m4 file missing?])]) |
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])dnl AX_REQUIRE_DEFINED |
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