Xcode 10: unable to attach DB error

When updating to Xcode 10, iOS static library target fails to build. Way how I am trying to build it is following:

xcodebuild -target TargetName -configuration Release clean build

With Xcode 9 everything runs smoothly, but when Xcode 10 is used for build, I am getting following error (after clean runs smoothly):

note: Using new build system

note: Planning build

note: Constructing build description Build system information error: unable to attach DB: error: accessing build database "/Users/uerceg/random-path/build/XCBuildData/build.db": database is locked Possibly there are two concurrent builds running in the same filesystem location.

** BUILD FAILED **

** BUILD FAILED **

The following build commands failed: PhaseScriptExecution MultiPlatform\ Build /Users/uerceg/random-path/build/Library.build/Release-iphoneos/LibraryTarget.build/Script-9DE7C9021AE68FA5001556E5.sh (1 failure)

This probably unrelated, but I noticed that new Xcode 10 build system flags duplicated Copy Bundle Resource Info.plist files as errors, so I did make sure that there're no duplicated entries, but probably this error is not related to this fact.

Does anyone have any idea what might be wrong?

Okay, seems like I managed to solve it. I was having /bin/sh script in Build Phases that was trying to build fat static library. In the script, I had OBJROOT path set like this:

OBJROOT="${OBJROOT}"

Seems like Xcode 10 and new build system changed some paths on the way and this line was the source of the issue. It needs to be adjusted to:

OBJROOT="${OBJROOT}/DependentBuilds"

After that, xcodebuild manages to build this target without issues with new build system introduced in Xcode 10.

I didn't get to this solution by myself, big thanks to Matt Gallagher and his post in here: https://github.com/mattgallagher/CwlSignal/issues/24#issuecomment-396931001

As requested by @TMin in comment, here's how my script looks like:

set -e

# If we're already inside this script then die
if [ -n "$RW_MULTIPLATFORM_BUILD_IN_PROGRESS" ]; then
exit 0
fi
export RW_MULTIPLATFORM_BUILD_IN_PROGRESS=1

RW_FRAMEWORK_NAME=${PROJECT_NAME}
RW_INPUT_STATIC_LIB="lib${PROJECT_NAME}.a"
RW_FRAMEWORK_LOCATION="${BUILT_PRODUCTS_DIR}/static/${RW_FRAMEWORK_NAME}Sdk.framework"

function build_static_library {
    echo "1"
    echo "${BUILD_DIR}"
    # Will rebuild the static library as specified
    #     build_static_library sdk
    xcrun xcodebuild -project "${PROJECT_FILE_PATH}" \
    -target "${TARGET_NAME}" \
    -configuration "${CONFIGURATION}" \
    -sdk "${1}" \
    ONLY_ACTIVE_ARCH=NO \
    BUILD_DIR="${BUILD_DIR}" \
    OBJROOT="${OBJROOT}" \
    BUILD_ROOT="${BUILD_ROOT}" \
    SYMROOT="${SYMROOT}" $ACTION
}

function make_fat_library {
    # Will smash 2 static libs together
    #     make_fat_library in1 in2 out
    xcrun lipo -create "${1}" "${2}" -output "${3}"
}

# 1 - Extract the platform (iphoneos/iphonesimulator) from the SDK name
if [[ "$SDK_NAME" =~ ([A-Za-z]+) ]]; then
RW_SDK_PLATFORM=${BASH_REMATCH[1]}
else
echo "Could not find platform name from SDK_NAME: $SDK_NAME"
exit 1
fi

# 2 - Extract the version from the SDK
if [[ "$SDK_NAME" =~ ([0-9]+.*$) ]]; then
RW_SDK_VERSION=${BASH_REMATCH[1]}
else
echo "Could not find sdk version from SDK_NAME: $SDK_NAME"
exit 1
fi

# 3 - Determine the other platform
if [ "$RW_SDK_PLATFORM" == "iphoneos" ]; then
RW_OTHER_PLATFORM=iphonesimulator
else
RW_OTHER_PLATFORM=iphoneos
fi

# 4 - Find the build directory
if [[ "$BUILT_PRODUCTS_DIR" =~ (.*)$RW_SDK_PLATFORM$ ]]; then
RW_OTHER_BUILT_PRODUCTS_DIR="${BASH_REMATCH[1]}${RW_OTHER_PLATFORM}"
else
echo "Could not find other platform build directory."
exit 1
fi

# Build the other platform.
build_static_library "${RW_OTHER_PLATFORM}${RW_SDK_VERSION}"

# If we're currently building for iphonesimulator, then need to rebuild
#   to ensure that we get both i386 and x86_64
if [ "$RW_SDK_PLATFORM" == "iphonesimulator" ]; then
build_static_library "${SDK_NAME}"
fi

# Join the 2 static libs into 1 and push into the .framework
make_fat_library "${BUILT_PRODUCTS_DIR}/${RW_INPUT_STATIC_LIB}" \
"${RW_OTHER_BUILT_PRODUCTS_DIR}/${RW_INPUT_STATIC_LIB}" \
"${RW_FRAMEWORK_LOCATION}/Versions/A/${RW_FRAMEWORK_NAME}Sdk"

# Ensure that the framework is present in both platform's build directories
cp -a "${RW_FRAMEWORK_LOCATION}/Versions/A/${RW_FRAMEWORK_NAME}Sdk" \
"${RW_OTHER_BUILT_PRODUCTS_DIR}/static/${RW_FRAMEWORK_NAME}Sdk.framework/Versions/A/${RW_FRAMEWORK_NAME}Sdk"

# Copy the framework to the project directory
ditto "${RW_FRAMEWORK_LOCATION}" "${SRCROOT}/Frameworks/static/${RW_FRAMEWORK_NAME}Sdk.framework"

Problem is in build_static_library method in this line:

OBJROOT="${OBJROOT}" \

Changing that line to:

OBJROOT="${OBJROOT}/DependantBuilds" \

solves the issue for me.

Open XCode File->Project Settings

Build System->Legacy Build System

Configure XCode of version 10.0 project settings can solve the problem.

If you use build script to build submodule's libraries like me. You also need to disable new build system in your build script explicitly by using -UseModernBuildSystem=NO in your xcodebuild command.

For example:

xcodebuild -configuration "${CONFIGURATION}" -project "${PROJECT_NAME}.xcodeproj" -target "${TARGET_NAME}" -sdk "${OTHER_SDK_TO_BUILD}" ${ACTION} RUN_CLANG_STATIC_ANALYZER=NO BUILD_DIR="${BUILD_DIR}" BUILD_ROOT="${BUILD_ROOT}" SYMROOT="${SYMROOT}" -UseModernBuildSystem=NO