Xcode 10: unable to attach DB error

Deleting the Derived Data worked for me. See how you can do it: https://programmingwithswift.com/delete-derived-data-xcode/

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

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.