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Improve CC_FOR_BUILD detection
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This commits simply uses CC as CC_FOR_BUILD and the same for
corresponding flags if we're not cross-compiling. This has a number of
benefits in this common case:
 - It avoids strange cases where very old compilers are used (#768).
 - Flags are consistently set for CC and CC_FOR_BUILD.
 - ./configure is faster.
 - You get compiler x consistently if you set CC=x; we got this wrong
   in CI in the past.

./configure warns if a _FOR_BUILD variable is set but ignored because
we're not cross-compiling.

The change exposed that //-style comments are used in gen_context.c,
which is also fixed by this commit.

This commit also reorganizes code in configure.ac to have a cleaner
separation of sections.
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@real-or-random
real-or-random committed Jan 2, 2021
1 parent aeb33fb commit 517c44c
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Showing 2 changed files with 98 additions and 62 deletions.
156 changes: 96 additions & 60 deletions configure.ac
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@ PKG_PROG_PKG_CONFIG
AC_PATH_TOOL(AR, ar)
AC_PATH_TOOL(RANLIB, ranlib)
AC_PATH_TOOL(STRIP, strip)
AX_PROG_CC_FOR_BUILD

AM_PROG_CC_C_O

Expand Down Expand Up @@ -89,6 +88,10 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
CFLAGS="$saved_CFLAGS"
])

###
### Parse config arguments
###

AC_ARG_ENABLE(benchmark,
AS_HELP_STRING([--enable-benchmark],[compile benchmark [default=yes]]),
[use_benchmark=$enableval],
Expand Down Expand Up @@ -180,6 +183,10 @@ AC_ARG_WITH([valgrind], [AS_HELP_STRING([--with-valgrind=yes|no|auto],
)],
[req_valgrind=$withval], [req_valgrind=auto])

###
### Handle config options
###

if test x"$req_valgrind" = x"no"; then
enable_valgrind=no
else
Expand All @@ -203,61 +210,6 @@ else
CFLAGS="-O2 $CFLAGS"
fi

if test x"$use_ecmult_static_precomputation" != x"no"; then
# Temporarily switch to an environment for the native compiler
save_cross_compiling=$cross_compiling
cross_compiling=no
SAVE_CC="$CC"
CC="$CC_FOR_BUILD"
SAVE_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS_FOR_BUILD"
SAVE_CPPFLAGS="$CPPFLAGS"
CPPFLAGS="$CPPFLAGS_FOR_BUILD"
SAVE_LDFLAGS="$LDFLAGS"
LDFLAGS="$LDFLAGS_FOR_BUILD"

warn_CFLAGS_FOR_BUILD="-Wall -Wextra -Wno-unused-function"
saved_CFLAGS="$CFLAGS"
CFLAGS="$warn_CFLAGS_FOR_BUILD $CFLAGS"
AC_MSG_CHECKING([if native ${CC_FOR_BUILD} supports ${warn_CFLAGS_FOR_BUILD}])
AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
[ AC_MSG_RESULT([yes]) ],
[ AC_MSG_RESULT([no])
CFLAGS="$saved_CFLAGS"
])

AC_MSG_CHECKING([for working native compiler: ${CC_FOR_BUILD}])
AC_RUN_IFELSE(
[AC_LANG_PROGRAM([], [])],
[working_native_cc=yes],
[working_native_cc=no],[:])

CFLAGS_FOR_BUILD="$CFLAGS"

# Restore the environment
cross_compiling=$save_cross_compiling
CC="$SAVE_CC"
CFLAGS="$SAVE_CFLAGS"
CPPFLAGS="$SAVE_CPPFLAGS"
LDFLAGS="$SAVE_LDFLAGS"

if test x"$working_native_cc" = x"no"; then
AC_MSG_RESULT([no])
set_precomp=no
m4_define([please_set_for_build], [Please set CC_FOR_BUILD, CFLAGS_FOR_BUILD, CPPFLAGS_FOR_BUILD, and/or LDFLAGS_FOR_BUILD.])
if test x"$use_ecmult_static_precomputation" = x"yes"; then
AC_MSG_ERROR([native compiler ${CC_FOR_BUILD} does not produce working binaries. please_set_for_build])
else
AC_MSG_WARN([Disabling statically generated ecmult table because the native compiler ${CC_FOR_BUILD} does not produce working binaries. please_set_for_build])
fi
else
AC_MSG_RESULT([yes])
set_precomp=yes
fi
else
set_precomp=no
fi

if test x"$req_asm" = x"auto"; then
SECP_64BIT_ASM_CHECK
if test x"$has_64bit_asm" = x"yes"; then
Expand Down Expand Up @@ -311,6 +263,79 @@ else
esac
fi

# This should come after all tests which modify CFLAGS and friends.
if test x"$use_ecmult_static_precomputation" != x"no"; then
if test x"$cross_compiling" = x"no"; then
set_precomp=yes
if test x"${CC_FOR_BUILD+x}${CFLAGS_FOR_BUILD+x}${CPPFLAGS_FOR_BUILD+x}${LDFLAGS_FOR_BUILD+x}" != x; then
AC_MSG_WARN([CC_FOR_BUILD, CFLAGS_FOR_BUILD, CPPFLAGS_FOR_BUILD, and/or LDFLAGS_FOR_BUILD is set but ignored because we are not cross-compiling.])
fi
# If we're not cross-compiling, simply use the same compiler for building the static precompation code.
CC_FOR_BUILD="$CC"
CFLAGS_FOR_BUILD="$CFLAGS"
CPPFLAGS_FOR_BUILD="$CPPFLAGS"
LDFLAGS_FOR_BUILD="$LDFLAGS"
else
AX_PROG_CC_FOR_BUILD

# Temporarily switch to an environment for the native compiler
save_cross_compiling=$cross_compiling
cross_compiling=no
SAVE_CC="$CC"
CC="$CC_FOR_BUILD"
SAVE_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS_FOR_BUILD"
SAVE_CPPFLAGS="$CPPFLAGS"
CPPFLAGS="$CPPFLAGS_FOR_BUILD"
SAVE_LDFLAGS="$LDFLAGS"
LDFLAGS="$LDFLAGS_FOR_BUILD"

warn_CFLAGS_FOR_BUILD="-Wall -Wextra -Wno-unused-function"
saved_CFLAGS="$CFLAGS"
CFLAGS="$warn_CFLAGS_FOR_BUILD $CFLAGS"
AC_MSG_CHECKING([if native ${CC_FOR_BUILD} supports ${warn_CFLAGS_FOR_BUILD}])
AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
[ AC_MSG_RESULT([yes]) ],
[ AC_MSG_RESULT([no])
CFLAGS="$saved_CFLAGS"
])

AC_MSG_CHECKING([for working native compiler: ${CC_FOR_BUILD}])
AC_RUN_IFELSE(
[AC_LANG_PROGRAM([], [])],
[working_native_cc=yes],
[working_native_cc=no],[:])

# Restore the environment
cross_compiling=$save_cross_compiling
CC="$SAVE_CC"
CFLAGS="$SAVE_CFLAGS"
CPPFLAGS="$SAVE_CPPFLAGS"
LDFLAGS="$SAVE_LDFLAGS"

if test x"$working_native_cc" = x"no"; then
AC_MSG_RESULT([no])
set_precomp=no
m4_define([please_set_for_build], [Please set CC_FOR_BUILD, CFLAGS_FOR_BUILD, CPPFLAGS_FOR_BUILD, and/or LDFLAGS_FOR_BUILD.])
if test x"$use_ecmult_static_precomputation" = x"yes"; then
AC_MSG_ERROR([native compiler ${CC_FOR_BUILD} does not produce working binaries. please_set_for_build])
else
AC_MSG_WARN([Disabling statically generated ecmult table because the native compiler ${CC_FOR_BUILD} does not produce working binaries. please_set_for_build])
fi
else
AC_MSG_RESULT([yes])
set_precomp=yes
fi
fi

AC_SUBST(CC_FOR_BUILD)
AC_SUBST(CFLAGS_FOR_BUILD)
AC_SUBST(CPPFLAGS_FOR_BUILD)
AC_SUBST(LDFLAGS_FOR_BUILD)
else
set_precomp=no
fi

# select assembly optimization
use_external_asm=no

Expand All @@ -328,6 +353,11 @@ no)
;;
esac

if test x"$use_external_asm" = x"yes"; then
AC_DEFINE(USE_EXTERNAL_ASM, 1, [Define this symbol if an external (non-inline) assembly implementation is used])
fi


# select wide multiplication implementation
case $set_widemul in
int128)
Expand Down Expand Up @@ -457,10 +487,6 @@ if test x"$enable_module_extrakeys" = x"yes"; then
AC_DEFINE(ENABLE_MODULE_EXTRAKEYS, 1, [Define this symbol to enable the extrakeys module])
fi

if test x"$use_external_asm" = x"yes"; then
AC_DEFINE(USE_EXTERNAL_ASM, 1, [Define this symbol if an external (non-inline) assembly implementation is used])
fi

if test x"$use_external_default_callbacks" = x"yes"; then
AC_DEFINE(USE_EXTERNAL_DEFAULT_CALLBACKS, 1, [Define this symbol if an external implementation of the default callbacks is used])
fi
Expand All @@ -484,6 +510,10 @@ else
fi
fi

###
### Generate output
###

AC_CONFIG_HEADERS([src/libsecp256k1-config.h])
AC_CONFIG_FILES([Makefile libsecp256k1.pc])
AC_SUBST(SECP_INCLUDES)
Expand Down Expand Up @@ -536,4 +566,10 @@ echo " CC = $CC"
echo " CFLAGS = $CFLAGS"
echo " CPPFLAGS = $CPPFLAGS"
echo " LDFLAGS = $LDFLAGS"
if test x"$cross_compiling" = x"yes"; then
echo " CC_FOR_BUILD = $CC_FOR_BUILD"
echo " CFLAGS_FOR_BUILD = $CFLAGS_FOR_BUILD"
echo " CPPFLAGS_FOR_BUILD = $CPPFLAGS_FOR_BUILD"
echo " LDFLAGS_FOR_BUILD = $LDFLAGS_FOR_BUILD"
fi
echo
4 changes: 2 additions & 2 deletions src/gen_context.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,8 +4,8 @@
* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
***********************************************************************/

// Autotools creates libsecp256k1-config.h, of which ECMULT_GEN_PREC_BITS is needed.
// ifndef guard so downstream users can define their own if they do not use autotools.
/* Autotools creates libsecp256k1-config.h, of which ECMULT_GEN_PREC_BITS is needed.
ifndef guard so downstream users can define their own if they do not use autotools. */
#if !defined(ECMULT_GEN_PREC_BITS)
#include "libsecp256k1-config.h"
#endif
Expand Down

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