dont do self test

[secp256k1.git] / configure.ac

diff --git a/configure.ac b/configure.ac
index 5a078e6c819198c5b3ba01d361e8ee195461a706..9969cfa343226f06cdb8899929fb3a96929332ee 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -8,13 +8,9 @@ AH_TOP([#define LIBSECP256K1_CONFIG_H])
 AH_BOTTOM([#endif /*LIBSECP256K1_CONFIG_H*/])
 AM_INIT_AUTOMAKE([foreign subdir-objects])
 
 AH_BOTTOM([#endif /*LIBSECP256K1_CONFIG_H*/])
 AM_INIT_AUTOMAKE([foreign subdir-objects])
 

-# Set -g if CFLAGS are not already set, which matches the default autoconf
-# behavior (see PROG_CC in the Autoconf manual) with the exception that we don't
-# set -O2 here because we set it in any case (see further down).
-: ${CFLAGS="-g"}

 LT_INIT
 
 LT_INIT
 

-dnl make the compilation flags quiet unless V=1 is used
+# Make the compilation flags quiet unless V=1 is used.

 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
 PKG_PROG_PKG_CONFIG
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
 PKG_PROG_PKG_CONFIG


@@ -22,9 +18,16 @@ PKG_PROG_PKG_CONFIG
 AC_PATH_TOOL(AR, ar)
 AC_PATH_TOOL(RANLIB, ranlib)
 AC_PATH_TOOL(STRIP, strip)
 AC_PATH_TOOL(AR, ar)
 AC_PATH_TOOL(RANLIB, ranlib)
 AC_PATH_TOOL(STRIP, strip)

-AX_PROG_CC_FOR_BUILD

 
 

+# Save definition of AC_PROG_CC because AM_PROG_CC_C_O in automake<=1.13 will
+# redefine AC_PROG_CC to exit with an error, which avoids the user calling it
+# accidently and screwing up the effect of AM_PROG_CC_C_O. However, we'll need
+# AC_PROG_CC later on in AX_PROG_CC_FOR_BUILD, where its usage is fine, and
+# we'll carefully make sure not to call AC_PROG_CC anywhere else.
+m4_copy([AC_PROG_CC], [saved_AC_PROG_CC])

 AM_PROG_CC_C_O
 AM_PROG_CC_C_O

+# Restore AC_PROG_CC
+m4_rename_force([saved_AC_PROG_CC], [AC_PROG_CC])

 
 AC_PROG_CC_C89
 if test x"$ac_cv_prog_cc_c89" = x"no"; then
 
 AC_PROG_CC_C89
 if test x"$ac_cv_prog_cc_c89" = x"no"; then


@@ -35,28 +38,26 @@ AM_PROG_AS
 case $host_os in
   *darwin*)
      if  test x$cross_compiling != xyes; then
 case $host_os in
   *darwin*)
      if  test x$cross_compiling != xyes; then

-       AC_PATH_PROG([BREW],brew,)
-       if test x$BREW != x; then
-         dnl These Homebrew packages may be keg-only, meaning that they won't be found
-         dnl in expected paths because they may conflict with system files. Ask
-         dnl Homebrew where each one is located, then adjust paths accordingly.
-
+       AC_CHECK_PROG([BREW], brew, brew)
+       if test x$BREW = xbrew; then
+         # These Homebrew packages may be keg-only, meaning that they won't be found
+         # in expected paths because they may conflict with system files. Ask
+         # Homebrew where each one is located, then adjust paths accordingly.

          openssl_prefix=`$BREW --prefix openssl 2>/dev/null`
          openssl_prefix=`$BREW --prefix openssl 2>/dev/null`

-         gmp_prefix=`$BREW --prefix gmp 2>/dev/null`
+         valgrind_prefix=`$BREW --prefix valgrind 2>/dev/null`

          if test x$openssl_prefix != x; then
            PKG_CONFIG_PATH="$openssl_prefix/lib/pkgconfig:$PKG_CONFIG_PATH"
            export PKG_CONFIG_PATH
            CRYPTO_CPPFLAGS="-I$openssl_prefix/include"
          fi
          if test x$openssl_prefix != x; then
            PKG_CONFIG_PATH="$openssl_prefix/lib/pkgconfig:$PKG_CONFIG_PATH"
            export PKG_CONFIG_PATH
            CRYPTO_CPPFLAGS="-I$openssl_prefix/include"
          fi

-         if test x$gmp_prefix != x; then
-           GMP_CPPFLAGS="-I$gmp_prefix/include"
-           GMP_LIBS="-L$gmp_prefix/lib"
+         if test x$valgrind_prefix != x; then
+           VALGRIND_CPPFLAGS="-I$valgrind_prefix/include"

          fi
        else
          fi
        else

-         AC_PATH_PROG([PORT],port,)
-         dnl if homebrew isn't installed and macports is, add the macports default paths
-         dnl as a last resort.
-         if test x$PORT != x; then
+         AC_CHECK_PROG([PORT], port, port)
+         # If homebrew isn't installed and macports is, add the macports default paths
+         # as a last resort.
+         if test x$PORT = xport; then

            CPPFLAGS="$CPPFLAGS -isystem /opt/local/include"
            LDFLAGS="$LDFLAGS -L/opt/local/lib"
          fi
            CPPFLAGS="$CPPFLAGS -isystem /opt/local/include"
            LDFLAGS="$LDFLAGS -L/opt/local/lib"
          fi


@@ -65,26 +66,45 @@ case $host_os in
    ;;
 esac
 
    ;;
 esac
 

-CFLAGS="-W $CFLAGS"
-
-warn_CFLAGS="-std=c89 -pedantic -Wall -Wextra -Wcast-align -Wnested-externs -Wshadow -Wstrict-prototypes -Wundef -Wno-unused-function -Wno-long-long -Wno-overlength-strings"
-saved_CFLAGS="$CFLAGS"
-CFLAGS="$warn_CFLAGS $CFLAGS"
-AC_MSG_CHECKING([if ${CC} supports ${warn_CFLAGS}])
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
-    [ AC_MSG_RESULT([yes]) ],
-    [ AC_MSG_RESULT([no])
-      CFLAGS="$saved_CFLAGS"
-    ])
-
-saved_CFLAGS="$CFLAGS"
-CFLAGS="-fvisibility=hidden $CFLAGS"
-AC_MSG_CHECKING([if ${CC} supports -fvisibility=hidden])
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
-    [ AC_MSG_RESULT([yes]) ],
-    [ AC_MSG_RESULT([no])
-      CFLAGS="$saved_CFLAGS"
-    ])
+# Try if some desirable compiler flags are supported and append them to SECP_CFLAGS.
+#
+# These are our own flags, so we append them to our own SECP_CFLAGS variable (instead of CFLAGS) as
+# recommended in the automake manual (Section "Flag Variables Ordering"). CFLAGS belongs to the user
+# and we are not supposed to touch it. In the Makefile, we will need to ensure that SECP_CFLAGS
+# is prepended to CFLAGS when invoking the compiler so that the user always has the last word (flag).
+#
+# Another advantage of not touching CFLAGS is that the contents of CFLAGS will be picked up by
+# libtool for compiling helper executables. For example, when compiling for Windows, libtool will
+# generate entire wrapper executables (instead of simple wrapper scripts as on Unix) to ensure
+# proper operation of uninstalled programs linked by libtool against the uninstalled shared library.
+# These executables are compiled from C source file for which our flags may not be appropriate,
+# e.g., -std=c89 flag has lead to undesirable warnings in the past.
+#
+# TODO We should analogously not touch CPPFLAGS and LDFLAGS but currently there are no issues.
+AC_DEFUN([SECP_TRY_APPEND_DEFAULT_CFLAGS], [
+    # Try to append -Werror=unknown-warning-option to CFLAGS temporarily. Otherwise clang will
+    # not error out if it gets unknown warning flags and the checks here will always succeed
+    # no matter if clang knows the flag or not.
+    SECP_TRY_APPEND_DEFAULT_CFLAGS_saved_CFLAGS="$CFLAGS"
+    SECP_TRY_APPEND_CFLAGS([-Werror=unknown-warning-option], CFLAGS)
+
+    SECP_TRY_APPEND_CFLAGS([-std=c89 -pedantic -Wno-long-long -Wnested-externs -Wshadow -Wstrict-prototypes -Wundef], $1) # GCC >= 3.0, -Wlong-long is implied by -pedantic.
+    SECP_TRY_APPEND_CFLAGS([-Wno-overlength-strings], $1) # GCC >= 4.2, -Woverlength-strings is implied by -pedantic.
+    SECP_TRY_APPEND_CFLAGS([-Wall], $1) # GCC >= 2.95 and probably many other compilers
+    SECP_TRY_APPEND_CFLAGS([-Wno-unused-function], $1) # GCC >= 3.0, -Wunused-function is implied by -Wall.
+    SECP_TRY_APPEND_CFLAGS([-Wextra], $1) # GCC >= 3.4, this is the newer name of -W, which we don't use because older GCCs will warn about unused functions.
+    SECP_TRY_APPEND_CFLAGS([-Wcast-align], $1) # GCC >= 2.95
+    SECP_TRY_APPEND_CFLAGS([-Wcast-align=strict], $1) # GCC >= 8.0
+    SECP_TRY_APPEND_CFLAGS([-Wconditional-uninitialized], $1) # Clang >= 3.0 only
+    SECP_TRY_APPEND_CFLAGS([-fvisibility=hidden], $1) # GCC >= 4.0
+
+    CFLAGS="$SECP_TRY_APPEND_DEFAULT_CFLAGS_saved_CFLAGS"
+])
+SECP_TRY_APPEND_DEFAULT_CFLAGS(SECP_CFLAGS)
+
+###
+### Define config arguments
+###

 
 AC_ARG_ENABLE(benchmark,
     AS_HELP_STRING([--enable-benchmark],[compile benchmark [default=yes]]),
 
 AC_ARG_ENABLE(benchmark,
     AS_HELP_STRING([--enable-benchmark],[compile benchmark [default=yes]]),


@@ -122,7 +142,7 @@ AC_ARG_ENABLE(ecmult_static_precomputation,
     [use_ecmult_static_precomputation=auto])
 
 AC_ARG_ENABLE(module_ecdh,
     [use_ecmult_static_precomputation=auto])
 
 AC_ARG_ENABLE(module_ecdh,

-    AS_HELP_STRING([--enable-module-ecdh],[enable ECDH shared secret computation (experimental)]),
+    AS_HELP_STRING([--enable-module-ecdh],[enable ECDH shared secret computation]),

     [enable_module_ecdh=$enableval],
     [enable_module_ecdh=no])
 
     [enable_module_ecdh=$enableval],
     [enable_module_ecdh=no])
 


@@ -146,13 +166,10 @@ AC_ARG_ENABLE(external_default_callbacks,
     [use_external_default_callbacks=$enableval],
     [use_external_default_callbacks=no])
 
     [use_external_default_callbacks=$enableval],
     [use_external_default_callbacks=no])
 

-dnl Test-only override of the (autodetected by the C code) "widemul" setting.
-dnl Legal values are int64 (for [u]int64_t), int128 (for [unsigned] __int128), and auto (the default).
+# Test-only override of the (autodetected by the C code) "widemul" setting.
+# Legal values are int64 (for [u]int64_t), int128 (for [unsigned] __int128), and auto (the default).

 AC_ARG_WITH([test-override-wide-multiply], [] ,[set_widemul=$withval], [set_widemul=auto])
 
 AC_ARG_WITH([test-override-wide-multiply], [] ,[set_widemul=$withval], [set_widemul=auto])
 

-AC_ARG_WITH([bignum], [AS_HELP_STRING([--with-bignum=gmp|no|auto],
-[bignum implementation to use [default=auto]])],[req_bignum=$withval], [req_bignum=auto])
-

 AC_ARG_WITH([asm], [AS_HELP_STRING([--with-asm=x86_64|arm|no|auto],
 [assembly optimizations to use (experimental: arm) [default=auto]])],[req_asm=$withval], [req_asm=auto])
 
 AC_ARG_WITH([asm], [AS_HELP_STRING([--with-asm=x86_64|arm|no|auto],
 [assembly optimizations to use (experimental: arm) [default=auto]])],[req_asm=$withval], [req_asm=auto])
 


@@ -177,79 +194,35 @@ AC_ARG_WITH([valgrind], [AS_HELP_STRING([--with-valgrind=yes|no|auto],
 )],
 [req_valgrind=$withval], [req_valgrind=auto])
 
 )],
 [req_valgrind=$withval], [req_valgrind=auto])
 

+###
+### Handle config options (except for modules)
+###
+

 if test x"$req_valgrind" = x"no"; then
   enable_valgrind=no
 else
 if test x"$req_valgrind" = x"no"; then
   enable_valgrind=no
 else

-  AC_CHECK_HEADER([valgrind/memcheck.h], [enable_valgrind=yes], [
+  SECP_VALGRIND_CHECK
+  if test x"$has_valgrind" != x"yes"; then

     if test x"$req_valgrind" = x"yes"; then
       AC_MSG_ERROR([Valgrind support explicitly requested but valgrind/memcheck.h header not available])
     fi
     enable_valgrind=no
     if test x"$req_valgrind" = x"yes"; then
       AC_MSG_ERROR([Valgrind support explicitly requested but valgrind/memcheck.h header not available])
     fi
     enable_valgrind=no

-  ], [])
+  else
+    enable_valgrind=yes
+  fi

 fi
 AM_CONDITIONAL([VALGRIND_ENABLED],[test "$enable_valgrind" = "yes"])
 
 if test x"$enable_coverage" = x"yes"; then
     AC_DEFINE(COVERAGE, 1, [Define this symbol to compile out all VERIFY code])
 fi
 AM_CONDITIONAL([VALGRIND_ENABLED],[test "$enable_valgrind" = "yes"])
 
 if test x"$enable_coverage" = x"yes"; then
     AC_DEFINE(COVERAGE, 1, [Define this symbol to compile out all VERIFY code])

-    CFLAGS="-O0 --coverage $CFLAGS"
+    SECP_CFLAGS="-O0 --coverage $SECP_CFLAGS"

     LDFLAGS="--coverage $LDFLAGS"
 else
     LDFLAGS="--coverage $LDFLAGS"
 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
+    # Most likely the CFLAGS already contain -O2 because that is autoconf's default.
+    # We still add it here because passing it twice is not an issue, and handling
+    # this case would just add unnecessary complexity (see #896).
+    SECP_CFLAGS="-O2 $SECP_CFLAGS"
+    SECP_CFLAGS_FOR_BUILD="-O2 $SECP_CFLAGS_FOR_BUILD"

 fi
 
 if test x"$req_asm" = x"auto"; then
 fi
 
 if test x"$req_asm" = x"auto"; then


@@ -279,33 +252,7 @@ else
   esac
 fi
 
   esac
 fi
 

-if test x"$req_bignum" = x"auto"; then
-  SECP_GMP_CHECK
-  if test x"$has_gmp" = x"yes"; then
-    set_bignum=gmp
-  fi
-
-  if test x"$set_bignum" = x; then
-    set_bignum=no
-  fi
-else
-  set_bignum=$req_bignum
-  case $set_bignum in
-  gmp)
-    SECP_GMP_CHECK
-    if test x"$has_gmp" != x"yes"; then
-      AC_MSG_ERROR([gmp bignum explicitly requested but libgmp not available])
-    fi
-    ;;
-  no)
-    ;;
-  *)
-    AC_MSG_ERROR([invalid bignum implementation selection])
-    ;;
-  esac
-fi
-
-# select assembly optimization
+# Select assembly optimization

 use_external_asm=no
 
 case $set_asm in
 use_external_asm=no
 
 case $set_asm in


@@ -322,7 +269,12 @@ no)
   ;;
 esac
 
   ;;
 esac
 

-# select wide multiplication implementation
+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)
   AC_DEFINE(USE_FORCE_WIDEMUL_INT128, 1, [Define this symbol to force the use of the (unsigned) __int128 based wide multiplication implementation])
 case $set_widemul in
 int128)
   AC_DEFINE(USE_FORCE_WIDEMUL_INT128, 1, [Define this symbol to force the use of the (unsigned) __int128 based wide multiplication implementation])


@@ -337,25 +289,7 @@ auto)
   ;;
 esac
 
   ;;
 esac
 

-# select bignum implementation
-case $set_bignum in
-gmp)
-  AC_DEFINE(HAVE_LIBGMP, 1, [Define this symbol if libgmp is installed])
-  AC_DEFINE(USE_NUM_GMP, 1, [Define this symbol to use the gmp implementation for num])
-  AC_DEFINE(USE_FIELD_INV_NUM, 1, [Define this symbol to use the num-based field inverse implementation])
-  AC_DEFINE(USE_SCALAR_INV_NUM, 1, [Define this symbol to use the num-based scalar inverse implementation])
-  ;;
-no)
-  AC_DEFINE(USE_NUM_NONE, 1, [Define this symbol to use no num implementation])
-  AC_DEFINE(USE_FIELD_INV_BUILTIN, 1, [Define this symbol to use the native field inverse implementation])
-  AC_DEFINE(USE_SCALAR_INV_BUILTIN, 1, [Define this symbol to use the native scalar inverse implementation])
-  ;;
-*)
-  AC_MSG_ERROR([invalid bignum implementation])
-  ;;
-esac
-
-#set ecmult window size
+# Set ecmult window size

 if test x"$req_ecmult_window" = x"auto"; then
   set_ecmult_window=15
 else
 if test x"$req_ecmult_window" = x"auto"; then
   set_ecmult_window=15
 else


@@ -377,7 +311,7 @@ case $set_ecmult_window in
   ;;
 esac
 
   ;;
 esac
 

-#set ecmult gen precision
+# Set ecmult gen precision

 if test x"$req_ecmult_gen_precision" = x"auto"; then
   set_ecmult_gen_precision=4
 else
 if test x"$req_ecmult_gen_precision" = x"auto"; then
   set_ecmult_gen_precision=4
 else


@@ -395,8 +329,8 @@ esac
 
 if test x"$use_tests" = x"yes"; then
   SECP_OPENSSL_CHECK
 
 if test x"$use_tests" = x"yes"; then
   SECP_OPENSSL_CHECK

-  if test x"$has_openssl_ec" = x"yes"; then
-    if test x"$enable_openssl_tests" != x"no"; then
+  if test x"$enable_openssl_tests" != x"no" && test x"$has_openssl_ec" = x"yes"; then
+      enable_openssl_tests=yes

       AC_DEFINE(ENABLE_OPENSSL_TESTS, 1, [Define this symbol if OpenSSL EC functions are available])
       SECP_TEST_INCLUDES="$SSL_CFLAGS $CRYPTO_CFLAGS $CRYPTO_CPPFLAGS"
       SECP_TEST_LIBS="$CRYPTO_LIBS"
       AC_DEFINE(ENABLE_OPENSSL_TESTS, 1, [Define this symbol if OpenSSL EC functions are available])
       SECP_TEST_INCLUDES="$SSL_CFLAGS $CRYPTO_CFLAGS $CRYPTO_CPPFLAGS"
       SECP_TEST_LIBS="$CRYPTO_LIBS"


@@ -406,27 +340,101 @@ if test x"$use_tests" = x"yes"; then
         SECP_TEST_LIBS="$SECP_TEST_LIBS -lgdi32"
         ;;
       esac
         SECP_TEST_LIBS="$SECP_TEST_LIBS -lgdi32"
         ;;
       esac

-    fi

   else
     if test x"$enable_openssl_tests" = x"yes"; then
       AC_MSG_ERROR([OpenSSL tests requested but OpenSSL with EC support is not available])
     fi
   else
     if test x"$enable_openssl_tests" = x"yes"; then
       AC_MSG_ERROR([OpenSSL tests requested but OpenSSL with EC support is not available])
     fi

+    enable_openssl_tests=no

   fi
 else
   if test x"$enable_openssl_tests" = x"yes"; then
     AC_MSG_ERROR([OpenSSL tests requested but tests are not enabled])
   fi
   fi
 else
   if test x"$enable_openssl_tests" = x"yes"; then
     AC_MSG_ERROR([OpenSSL tests requested but tests are not enabled])
   fi

+  enable_openssl_tests=no

 fi
 
 fi
 

-if test x"$set_bignum" = x"gmp"; then
-  SECP_LIBS="$SECP_LIBS $GMP_LIBS"
-  SECP_INCLUDES="$SECP_INCLUDES $GMP_CPPFLAGS"
+if test x"$enable_valgrind" = x"yes"; then
+  SECP_INCLUDES="$SECP_INCLUDES $VALGRIND_CPPFLAGS"
+fi
+
+# Add -Werror and similar flags passed from the outside (for testing, e.g., in CI)
+SECP_CFLAGS="$SECP_CFLAGS $WERROR_CFLAGS"
+
+# Handle static precomputation (after everything which modifies CFLAGS and friends)
+if test x"$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"
+    CPPFLAGS_FOR_BUILD="$CPPFLAGS"
+    SECP_CFLAGS_FOR_BUILD="$SECP_CFLAGS"
+    CFLAGS_FOR_BUILD="$CFLAGS"
+    LDFLAGS_FOR_BUILD="$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="$CC_FOR_BUILD"
+    SAVE_CPPFLAGS="$CPPFLAGS"
+    CPPFLAGS="$CPPFLAGS_FOR_BUILD"
+    SAVE_CFLAGS="$CFLAGS"
+    CFLAGS="$CFLAGS_FOR_BUILD"
+    SAVE_LDFLAGS="$LDFLAGS"
+    LDFLAGS="$LDFLAGS_FOR_BUILD"
+
+    SECP_TRY_APPEND_DEFAULT_CFLAGS(SECP_CFLAGS_FOR_BUILD)
+
+    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="$SAVE_CC"
+    CPPFLAGS="$SAVE_CPPFLAGS"
+    CFLAGS="$SAVE_CFLAGS"
+    LDFLAGS="$SAVE_LDFLAGS"
+
+    if test x"$working_native_cc" = x"no"; then
+      AC_MSG_RESULT([no])
+      set_precomp=no
+      m4_define([please_set_for_build], [Please set CC_FOR_BUILD, CPPFLAGS_FOR_BUILD, CFLAGS_FOR_BUILD, and/or LDFLAGS_FOR_BUILD.])
+      if test x"$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(CPPFLAGS_FOR_BUILD)
+  AC_SUBST(SECP_CFLAGS_FOR_BUILD)
+  AC_SUBST(CFLAGS_FOR_BUILD)
+  AC_SUBST(LDFLAGS_FOR_BUILD)
+else
+  set_precomp=no

 fi
 
 if test x"$set_precomp" = x"yes"; then
   AC_DEFINE(USE_ECMULT_STATIC_PRECOMPUTATION, 1, [Define this symbol to use a statically generated ecmult table])
 fi
 
 fi
 
 if test x"$set_precomp" = x"yes"; then
   AC_DEFINE(USE_ECMULT_STATIC_PRECOMPUTATION, 1, [Define this symbol to use a statically generated ecmult table])
 fi
 

+###
+### Handle module options
+###
+

 if test x"$enable_module_ecdh" = x"yes"; then
   AC_DEFINE(ENABLE_MODULE_ECDH, 1, [Define this symbol to enable the ECDH module])
 fi
 if test x"$enable_module_ecdh" = x"yes"; then
   AC_DEFINE(ENABLE_MODULE_ECDH, 1, [Define this symbol to enable the ECDH module])
 fi


@@ -446,26 +454,22 @@ if test x"$enable_module_extrakeys" = x"yes"; then
   AC_DEFINE(ENABLE_MODULE_EXTRAKEYS, 1, [Define this symbol to enable the extrakeys module])
 fi
 
   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
 
 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
 

+###
+### Check for --enable-experimental if necessary
+###
+

 if test x"$enable_experimental" = x"yes"; then
   AC_MSG_NOTICE([******])
   AC_MSG_NOTICE([WARNING: experimental build])
   AC_MSG_NOTICE([Experimental features do not have stable APIs or properties, and may not be safe for production use.])
 if test x"$enable_experimental" = x"yes"; then
   AC_MSG_NOTICE([******])
   AC_MSG_NOTICE([WARNING: experimental build])
   AC_MSG_NOTICE([Experimental features do not have stable APIs or properties, and may not be safe for production use.])

-  AC_MSG_NOTICE([Building ECDH module: $enable_module_ecdh])

   AC_MSG_NOTICE([Building extrakeys module: $enable_module_extrakeys])
   AC_MSG_NOTICE([Building schnorrsig module: $enable_module_schnorrsig])
   AC_MSG_NOTICE([******])
 else
   AC_MSG_NOTICE([Building extrakeys module: $enable_module_extrakeys])
   AC_MSG_NOTICE([Building schnorrsig module: $enable_module_schnorrsig])
   AC_MSG_NOTICE([******])
 else

-  if test x"$enable_module_ecdh" = x"yes"; then
-    AC_MSG_ERROR([ECDH module is experimental. Use --enable-experimental to allow.])
-  fi

   if test x"$enable_module_extrakeys" = x"yes"; then
     AC_MSG_ERROR([extrakeys module is experimental. Use --enable-experimental to allow.])
   fi
   if test x"$enable_module_extrakeys" = x"yes"; then
     AC_MSG_ERROR([extrakeys module is experimental. Use --enable-experimental to allow.])
   fi


@@ -477,12 +481,17 @@ else
   fi
 fi
 
   fi
 fi
 

+###
+### Generate output
+###
+

 AC_CONFIG_HEADERS([src/libsecp256k1-config.h])
 AC_CONFIG_FILES([Makefile libsecp256k1.pc])
 AC_SUBST(SECP_INCLUDES)
 AC_SUBST(SECP_LIBS)
 AC_SUBST(SECP_TEST_LIBS)
 AC_SUBST(SECP_TEST_INCLUDES)
 AC_CONFIG_HEADERS([src/libsecp256k1-config.h])
 AC_CONFIG_FILES([Makefile libsecp256k1.pc])
 AC_SUBST(SECP_INCLUDES)
 AC_SUBST(SECP_LIBS)
 AC_SUBST(SECP_TEST_LIBS)
 AC_SUBST(SECP_TEST_INCLUDES)

+AC_SUBST(SECP_CFLAGS)

 AM_CONDITIONAL([ENABLE_COVERAGE], [test x"$enable_coverage" = x"yes"])
 AM_CONDITIONAL([USE_TESTS], [test x"$use_tests" != x"no"])
 AM_CONDITIONAL([USE_EXHAUSTIVE_TESTS], [test x"$use_exhaustive_tests" != x"no"])
 AM_CONDITIONAL([ENABLE_COVERAGE], [test x"$enable_coverage" = x"yes"])
 AM_CONDITIONAL([USE_TESTS], [test x"$use_tests" != x"no"])
 AM_CONDITIONAL([USE_EXHAUSTIVE_TESTS], [test x"$use_exhaustive_tests" != x"no"])


@@ -495,7 +504,7 @@ AM_CONDITIONAL([ENABLE_MODULE_SCHNORRSIG], [test x"$enable_module_schnorrsig" =
 AM_CONDITIONAL([USE_EXTERNAL_ASM], [test x"$use_external_asm" = x"yes"])
 AM_CONDITIONAL([USE_ASM_ARM], [test x"$set_asm" = x"arm"])
 
 AM_CONDITIONAL([USE_EXTERNAL_ASM], [test x"$use_external_asm" = x"yes"])
 AM_CONDITIONAL([USE_ASM_ARM], [test x"$set_asm" = x"arm"])
 

-dnl make sure nothing new is exported so that we don't break the cache
+# Make sure nothing new is exported so that we don't break the cache.

 PKGCONFIG_PATH_TEMP="$PKG_CONFIG_PATH"
 unset PKG_CONFIG_PATH
 PKG_CONFIG_PATH="$PKGCONFIG_PATH_TEMP"
 PKGCONFIG_PATH_TEMP="$PKG_CONFIG_PATH"
 unset PKG_CONFIG_PATH
 PKG_CONFIG_PATH="$PKGCONFIG_PATH_TEMP"


@@ -507,6 +516,8 @@ echo "Build Options:"
 echo "  with ecmult precomp     = $set_precomp"
 echo "  with external callbacks = $use_external_default_callbacks"
 echo "  with benchmarks         = $use_benchmark"
 echo "  with ecmult precomp     = $set_precomp"
 echo "  with external callbacks = $use_external_default_callbacks"
 echo "  with benchmarks         = $use_benchmark"

+echo "  with tests              = $use_tests"
+echo "  with openssl tests      = $enable_openssl_tests"

 echo "  with coverage           = $enable_coverage"
 echo "  module ecdh             = $enable_module_ecdh"
 echo "  module recovery         = $enable_module_recovery"
 echo "  with coverage           = $enable_coverage"
 echo "  module ecdh             = $enable_module_ecdh"
 echo "  module recovery         = $enable_module_recovery"


@@ -514,17 +525,24 @@ echo "  module extrakeys        = $enable_module_extrakeys"
 echo "  module schnorrsig       = $enable_module_schnorrsig"
 echo
 echo "  asm                     = $set_asm"
 echo "  module schnorrsig       = $enable_module_schnorrsig"
 echo
 echo "  asm                     = $set_asm"

-echo "  bignum                  = $set_bignum"

 echo "  ecmult window size      = $set_ecmult_window"
 echo "  ecmult gen prec. bits   = $set_ecmult_gen_precision"
 echo "  ecmult window size      = $set_ecmult_window"
 echo "  ecmult gen prec. bits   = $set_ecmult_gen_precision"

-dnl Hide test-only options unless they're used.
+# Hide test-only options unless they're used.

 if test x"$set_widemul" != xauto; then
 echo "  wide multiplication     = $set_widemul"
 fi
 echo
 echo "  valgrind                = $enable_valgrind"
 echo "  CC                      = $CC"
 if test x"$set_widemul" != xauto; then
 echo "  wide multiplication     = $set_widemul"
 fi
 echo
 echo "  valgrind                = $enable_valgrind"
 echo "  CC                      = $CC"

-echo "  CFLAGS                  = $CFLAGS"

 echo "  CPPFLAGS                = $CPPFLAGS"
 echo "  CPPFLAGS                = $CPPFLAGS"

+echo "  SECP_CFLAGS             = $SECP_CFLAGS"
+echo "  CFLAGS                  = $CFLAGS"

 echo "  LDFLAGS                 = $LDFLAGS"
 echo
 echo "  LDFLAGS                 = $LDFLAGS"
 echo

+if test x"$set_precomp" = x"yes"; then
+echo "  CC_FOR_BUILD            = $CC_FOR_BUILD"
+echo "  CPPFLAGS_FOR_BUILD      = $CPPFLAGS_FOR_BUILD"
+echo "  SECP_CFLAGS_FOR_BUILD   = $SECP_CFLAGS_FOR_BUILD"
+echo "  CFLAGS_FOR_BUILD        = $CFLAGS_FOR_BUILD"
+echo "  LDFLAGS_FOR_BUILD       = $LDFLAGS_FOR_BUILD"
+fi