Try to use qemu for big endian test on travis

.travis.yml

@@ -1,8 +1,4 @@
 language: c
-os:
-  - linux
-  - osx
-
 dist: bionic
 # Valgrind currently supports upto macOS 10.13, the latest xcode of that version is 10.1
 osx_image: xcode10.1
@@ -12,77 +8,89 @@ addons:
       - libgmp-dev
       - valgrind
       - libtool-bin
-compiler:
-  - clang
-  - gcc
+services:
+  - docker
+
+#os:
+#  - linux
+#  - osx
+#compiler:
+#  - clang
+#  - gcc
 env:
   global:
     - WIDEMUL=auto  BIGNUM=auto  STATICPRECOMPUTATION=yes  ECMULTGENPRECISION=auto  ASM=no  BUILD=check  WITH_VALGRIND=yes RUN_VALGRIND=no EXTRAFLAGS=  HOST=  ECDH=no  RECOVERY=no SCHNORRSIG=no EXPERIMENTAL=no CTIMETEST=yes BENCH=yes ITERS=2
-  matrix:
-    - WIDEMUL=int64   RECOVERY=yes
-    - WIDEMUL=int64   ECDH=yes  EXPERIMENTAL=yes SCHNORRSIG=yes
-    - WIDEMUL=int128
-    - WIDEMUL=int128  RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes
-    - WIDEMUL=int128  ECDH=yes EXPERIMENTAL=yes SCHNORRSIG=yes
-    - WIDEMUL=int128                    ASM=x86_64
-    - BIGNUM=no
-    - BIGNUM=no       RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes
-    - BIGNUM=no       STATICPRECOMPUTATION=no
-    - BUILD=distcheck WITH_VALGRIND=no CTIMETEST=no BENCH=no
-    - CPPFLAGS=-DDETERMINISTIC
-    - CFLAGS=-O0 CTIMETEST=no
-    - ECMULTGENPRECISION=2
-    - ECMULTGENPRECISION=8
-    - RUN_VALGRIND=yes BIGNUM=no ASM=x86_64 ECDH=yes  RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes EXTRAFLAGS="--disable-openssl-tests" BUILD=
+#  matrix:
+#    - WIDEMUL=int64   RECOVERY=yes
+#    - WIDEMUL=int64   ECDH=yes  EXPERIMENTAL=yes SCHNORRSIG=yes
+#    - WIDEMUL=int128
+#    - WIDEMUL=int128  RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes
+#    - WIDEMUL=int128  ECDH=yes EXPERIMENTAL=yes SCHNORRSIG=yes
+#    - WIDEMUL=int128                    ASM=x86_64
+#    - BIGNUM=no
+#    - BIGNUM=no       RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes
+#    - BIGNUM=no       STATICPRECOMPUTATION=no
+#    - BUILD=distcheck WITH_VALGRIND=no CTIMETEST=no BENCH=no
+#    - CPPFLAGS=-DDETERMINISTIC
+#    - CFLAGS=-O0 CTIMETEST=no
+#    - ECMULTGENPRECISION=2
+#    - ECMULTGENPRECISION=8
+#    - RUN_VALGRIND=yes BIGNUM=no ASM=x86_64 ECDH=yes  RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes EXTRAFLAGS="--disable-openssl-tests" BUILD=
+
 matrix:
   fast_finish: true
   include:
-    - compiler: clang
-      os: linux
-      env: HOST=i686-linux-gnu
-      addons:
-        apt:
-          packages:
-            - gcc-multilib
-            - libgmp-dev:i386
-            - valgrind
-            - libtool-bin
-            - libc6-dbg:i386
-    - compiler: clang
-      env: HOST=i686-linux-gnu
-      os: linux
-      addons:
-        apt:
-          packages:
-            - gcc-multilib
-            - valgrind
-            - libtool-bin
-            - libc6-dbg:i386
-    - compiler: gcc
-      env: HOST=i686-linux-gnu
-      os: linux
-      addons:
-        apt:
-          packages:
-            - gcc-multilib
-            - valgrind
-            - libtool-bin
-            - libc6-dbg:i386
+#    - compiler: clang
+#      os: linux
+#      env: HOST=i686-linux-gnu
+#      addons:
+#        apt:
+#          packages:
+#            - gcc-multilib
+#            - libgmp-dev:i386
+#            - valgrind
+#            - libtool-bin
+#            - libc6-dbg:i386
+#    - compiler: clang
+#      env: HOST=i686-linux-gnu
+#      os: linux
+#      addons:
+#        apt:
+#          packages:
+#            - gcc-multilib
+#            - valgrind
+#            - libtool-bin
+#            - libc6-dbg:i386
+#    - compiler: gcc
+#      env: HOST=i686-linux-gnu
+#      os: linux
+#      addons:
+#        apt:
+#          packages:
+#            - gcc-multilib
+#            - valgrind
+#            - libtool-bin
+#            - libc6-dbg:i386
+#    - compiler: gcc
+#      os: linux
+#      env: HOST=i686-linux-gnu
+#      addons:
+#        apt:
+#          packages:
+#            - gcc-multilib
+#            - libgmp-dev:i386
+#            - valgrind
+#            - libtool-bin
+#            - libc6-dbg:i386
+    # S390x build (big endian system)
     - compiler: gcc
-      os: linux
-      env: HOST=i686-linux-gnu
+      env: HOST=s390x-unknown-linux-gnu ECDH=yes RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes CTIMETEST= BENCH=no WITH_VALGRIND=no BUILD= QEMU=s390x
       addons:
         apt:
           packages:
-            - gcc-multilib
-            - libgmp-dev:i386
-            - valgrind
             - libtool-bin
-            - libc6-dbg:i386
-    # S390x build (big endian system)
-    - compiler: gcc
-      env: HOST=s390x-unknown-linux-gnu ECDH=yes RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes CTIMETEST=
-      arch: s390x
+            - gcc-s390x-linux-gnu
+            - libc6-dev-s390x-cross
 
 # We use this to install macOS dependencies instead of the built in `homebrew` plugin,
 # because in xcode earlier than 11 they have a bug requiring updating the system which overall takes ~8 minutes.
@@ -94,6 +102,8 @@ before_script: ./autogen.sh
 
 # travis auto terminates jobs that go for 10 minutes without printing to stdout, but travis_wait doesn't work well with forking programs like valgrind (https://docs.travis-ci.com/user/common-build-problems/#build-times-out-because-no-output-was-received https://github.com/bitcoin-core/secp256k1/pull/750#issuecomment-623476860)
 script:
+  - if [ -n "$QEMU" ]; then docker run --rm --privileged multiarch/qemu-user-static --reset -p yes; fi
+  - cat /proc/sys/fs/binfmt_misc/qemu-s390x
   - function keep_alive() { while true; do echo -en "\a"; sleep 60; done }
   - keep_alive &
   - ./contrib/travis.sh
@@ -106,3 +116,4 @@ after_script:
     - cat ./bench.log
     - $CC --version
     - valgrind --version
+    - ls /usr/bin/qemu*

contrib/travis.sh

@@ -21,13 +21,23 @@ fi
     --with-valgrind="$WITH_VALGRIND" \
     --host="$HOST" $EXTRAFLAGS
 
+make -j2
+
 if [ -n "$BUILD" ]
 then
-    make -j2 "$BUILD"
+    make "$BUILD"
 fi
+
+if [ -n "$QEMU" ]
+then
+    qemu_run() { docker run --rm -t -v "${PWD}:/mnt/secp256k1" -w /mnt/secp256k1 $QEMU/ubuntu "$@"; }
+    qemu_run ls /mnt/secp256k1
+    qemu_run ./tests
+    qemu_run ./exhaustive_tests
+fi
+
 if [ "$RUN_VALGRIND" = "yes" ]
 then
-    make -j2
     # the `--error-exitcode` is required to make the test fail if valgrind found errors, otherwise it'll return 0 (http://valgrind.org/docs/manual/manual-core.html)
     valgrind --error-exitcode=42 ./tests 16
     valgrind --error-exitcode=42 ./exhaustive_tests