Add simple static checker using clang-query

.gitignore

@@ -33,6 +33,8 @@ libtool
 *~
 *.log
 *.trs
+compile_commands.commands.json
+compile_commands.json
 src/libsecp256k1-config.h
 src/libsecp256k1-config.h.in
 src/ecmult_static_context.h

.travis.yml

@@ -12,6 +12,7 @@ addons:
       - libgmp-dev
       - valgrind
       - libtool-bin
+      - bear
 compiler:
   - clang
   - gcc
@@ -47,6 +48,7 @@ matrix:
             - libgmp-dev:i386
             - valgrind
             - libtool-bin
+            - bear
             - libc6-dbg:i386
     - compiler: clang
       env: HOST=i686-linux-gnu
@@ -57,6 +59,7 @@ matrix:
             - gcc-multilib
             - valgrind
             - libtool-bin
+            - bear
             - libc6-dbg:i386
     - compiler: gcc
       env: HOST=i686-linux-gnu
@@ -104,5 +107,6 @@ after_script:
     - cat ./exhaustive_tests.log
     - cat ./valgrind_ctime_test.log
     - cat ./bench.log
+    - cat ./compile_commands.json
     - $CC --version
     - valgrind --version

clang-query.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+set -u
+
+matcher=$(cat <<'EOF'
+set print-matcher true
+
+# expressions of any floating point type (unless in a system header)
+match expr(allOf(unless(isExpansionInSystemHeader()), hasType(realFloatingPointType())))
+
+# calls to memcmp (secp256k1_memcmp_var should be used instead)
+match callExpr(callee(functionDecl(hasName("memcmp"))))
+
+quit
+EOF
+)
+
+output=$(echo "$matcher" | clang-query src/*.c)
+status=$?
+if [ $status -ne 0 ]
+then
+    exit $status
+fi
+echo "$output"
+# For some reason, clang-query returns a zero status even if clang failed to process the file.
+# This is not a big issue. If clang errors, we'll notice that when trying to compile with clang anyway.
+# We still try to catch this case by grepping also for "error:".
+echo "$output" | grep -qE "^Match #|error:"
+if [ $? -eq 0 ]
+then
+    exit 1
+fi
+
+echo
+exit 0

contrib/travis.sh

@@ -23,7 +23,14 @@ fi
 
 if [ -n "$BUILD" ]
 then
-    make -j2 "$BUILD"
+   if [ "$TRAVIS_COMPILER" = "clang" ]
+   then
+       # Use bear to generate compile_commands.json
+       # This needs to be the first make command because otherwise make does not invoke the compiler because the files are up to date.
+       # This needs to be a separate make command because bear does not seem to like our "make check".
+       bear -- make -j2
+   fi
+   make -j2 "$BUILD"
 fi
 if [ "$RUN_VALGRIND" = "yes" ]
 then
@@ -66,3 +73,9 @@ if [ "$CTIMETEST" = "yes" ]
 then
     ./libtool --mode=execute valgrind --error-exitcode=42 ./valgrind_ctime_test > valgrind_ctime_test.log 2>&1
 fi
+
+# This would also run on gcc builds but there's no need to run it for both compilers.
+if [ "$TRAVIS_COMPILER" = "clang" ]
+then
+    ./clang-query.sh
+fi