Building CyanogenMod 13: customizing build.prop via makefile

Question

Following this guide on CM Wiki, I've been compiling CM for my own devices for more than a year now, but that does nothing more than recreating nightly builds. I always wanted to venture beyond the basics and today I got my hands on making some first steps.

What I'm planning to do right now is to customize /system/build.prop prior to building, as opposed to modifying it after flashing. I did some research and identified some scripts and makefiles responsible for generating it, and the one makefile in question is vendor/cm/config/common.mk. The section I'm looking to modify alters the "CyanogenMod version" field displayed in Settings-About, as in the pic below:

common.mk has these lines corresponding to it (slightly modified to shorten):

ifeq ($(CM_BUILDTYPE), RELEASE)
    ifndef TARGET_VENDOR_RELEASE_BUILD_ID
        CM_VERSION := $(PRODUCT_VERSION_MAJOR).$(PRODUCT_VERSION_MINOR).$(PRODUCT_VERSION_MAINTENANCE)$(PRODUCT_VERSION_DEVICE_SPECIFIC)-$(CM_BUILD)
    else
        ifeq ($(TARGET_BUILD_VARIANT),user)
            ifeq ($(CM_VERSION_MAINTENANCE),0)
                CM_VERSION := $(PRODUCT_VERSION_MAJOR).$(PRODUCT_VERSION_MINOR)-$(TARGET_VENDOR_RELEASE_BUILD_ID)-$(CM_BUILD)
            else
                CM_VERSION := $(PRODUCT_VERSION_MAJOR).$(PRODUCT_VERSION_MINOR).$(CM_VERSION_MAINTENANCE)-$(TARGET_VENDOR_RELEASE_BUILD_ID)-$(CM_BUILD)
            endif
        else
            CM_VERSION := $(PRODUCT_VERSION_MAJOR).$(PRODUCT_VERSION_MINOR).$(PRODUCT_VERSION_MAINTENANCE)$(PRODUCT_VERSION_DEVICE_SPECIFIC)-$(CM_BUILD)
        endif
    endif
else
    ifeq ($(CM_VERSION_MAINTENANCE),0)
        CM_VERSION := $(PRODUCT_VERSION_MAJOR).$(PRODUCT_VERSION_MINOR)-$(shell date -u +%Y%m%d)-$(CM_BUILDTYPE)$(CM_EXTRAVERSION)-$(CM_BUILD)
    else
        CM_VERSION := $(PRODUCT_VERSION_MAJOR).$(PRODUCT_VERSION_MINOR).$(CM_VERSION_MAINTENANCE)-$(shell date -u +%Y%m%d)-$(CM_BUILDTYPE)$(CM_EXTRAVERSION)-$(CM_BUILD)
    endif
endif

PRODUCT_PROPERTY_OVERRIDES += \
  ro.cm.version=$(CM_VERSION) \
  ro.cm.releasetype=$(CM_BUILDTYPE) \
  ro.modversion=$(CM_VERSION) \
  ro.cm.display.version=$(CM_VERSION)

Now I want to define another variable with space that stores the custom string that I want to display in that field, for example "CM13 FOO BAR", so I'd write this:

ifndef CM_VERSION_CUSTOM
    CM_VERSION_CUSTOM := CM13 FOO BAR
endif

...and assign CM_VERSION_CUSTOM to where CM_VERSION applies.

In practise this doesn't work at all - the string was outputted to /build.prop incorrectly, sometimes as if each space is a newline, sometimes as if the contents after the 1st space doesn't exist, like this:

ro.cm.version=CM13
FOO
BAR
ro.modversion=CM13
ro.cm.display.version=CM13

I tried adding quotes (' and " tested), either to the string definition or to where CM_VERSION CUSTOM was referenced (like "$(CM_VERSION_CUSTOM)"), but none helped. I'm not familiar with makefile at all, so I'm at a loss right now. Can someone point me in the right way?

score 0 · Accepted Answer · answered Oct 19 '16 at 14:59

I ended up just writing a shell script for the purpose. I package the script inside a flashable zip and let updater-script call the script. The script itself goes something like this:

#!/sbin/sh

CM_VER="CyanogenMod 12.1 Nightly CGMod"
sed -i "s/ro.cm.version=.*/ro.cm.version=$CM_VER/g" /system/build.prop

This not only allows me to modify this property, but also others like build type, date and others (with the help of grep) that are hard to touch before building.

Building CyanogenMod 13: customizing build.prop via makefile

1 Answers1