Kernel compilation flags – A pain in the a*

So I pulled snq’s froyo kernel (that guy is a marvel)..

Some kernel compilation errors:

1. Treat warnings as errors-Solved by removing the string “-Werror” from all Makefiles of the file which failed to compile. Some people had said that the real error (Array out of bounds warning) was because of gcc optimizations. But putting -O2 to -O0 didnt do a thing. This can also be done from menuconfig: System type>Force warnings as errors
2. No of jobs – ought not to exceed 50.
3. “warning: variable set but not used [-Wunused-but-set-variable]”-Look at KBUILD_CFLAGS in the main Makefile. Add -Wno-unused-but-set-variable to the existing set of flags. You can alternately add a line that says

Note the following from gcc manual:

Refer Preprocessor options

• -Werror[/code]Make all warnings into hard errors. Source code which triggers warnings will be rejected.

• -w[/code]Inhibit all warning messages.

• -Werror[/code]Make all warnings into errors.

• -Werror=[/code]Make the specified warning into an error. The specifier for a warning is appended, for example -Werror=switch turns the warnings controlled by -Wswitch into errors. This switch takes a negative form, to be used to negate -Werror for specific warnings, for example -Wno-error=switch makes -Wswitch warnings not be errors, even when -Werror is in effect. You can use the -fdiagnostics-show-option option to have each controllable warning amended with the option which controls it, to determine what to use with this option.

Though the -Wunused-but-set-variable is not a real issue in itself, it generates so much "noise" that you may miss actual make errors.

This is what I was talking about in No 1.

drivers/net/wireless/bcm4329_204/wl_iw.c: In function 'wl_iw_set_pmksa':

drivers/net/wireless/bcm4329_204/wl_iw.c:5075:5: error: array subscript is above array bounds [-Werror=array-bounds]

drivers/net/wireless/bcm4329_204/wl_iw.c:5078:5: error: array subscript is above array bounds [-Werror=array-bounds]

[/code]

Solution:

Edit drivers/net/wireless/bcm4329_204/Makefile
Locate -Werror within DHDCFLAGS, and delete it.
DHDCFLAGS = -DLINUX -DBCMDRIVER -DBCMDONGLEHOST -DDHDTHREAD -DBCMWPA2

-DUNRELEASEDCHIP -Dlinux -DDHD_SDALIGN=64 -DMAX_HDR_READ=64

-DDHD_FIRSTREAD=64 -DDHD_GPL -DDHD_SCHED -DBDC -DTOE -DDHD_BCMEVENTS

-DSHOW_EVENTS -DBCMSDIO -DDHD_GPL -DBCMLXSDMMC -DBCMPLATFORM_BUS

-Wall -Wstrict-prototypes -Werror -DOOB_INTR_ONLY -DCUSTOMER_HW2

-DDHD_USE_STATIC_BUF -DMMC_SDIO_ABORT -DWLAN_PFN -DWLAN_PROTECT

-DBCMWAPI_WPI

[/code]

This will prevent gcc from treating mere warnings as errors.
-
Joel G Mathew
Joel G Mathew, known in tech circles by the pseudonym Droidzone, is an opensource and programming enthusiast.
He is a full stack developer, whose favorite languages are currently Python and Vue.js. He is also fluent in Javascript, Flutter/Dart, Perl, PHP, SQL, C and bash shell scripting. He loves Linux, and can often be found tinkering with linux kernel code, and source code for GNU applications. He used to be an active developer on XDA forums, and his tinkered ROMS used to be very popular in the early 2000s.
His favorite pastime is grappling with GNU compilers, discovering newer Linux secrets, writing scripts, hacking roms, and programs (nothing illegal), reading, blogging. and testing out the latest gadgets.
When away from the tech world, Dr Joel G. Mathew is a practising ENT Surgeon, busy with surgeries and clinical practise.