Wanted to try Windows 10’s Windows On Linux subsystem to see if we can test mingw built toolchain binaries using the usual Dejagnu/expect/tcl testsuite runner. First step, of course, was to get my hands on a Windows 10 ISO. I didn’t have a spare machine lying around, so I decided to try this on a VM. I had a CentOS machine available that I could logon remotely, so I yum installed VirtualBox-5.0 after following the instructions at https://wiki.centos.org/HowTos/Virtualization/VirtualBox.
Read more →
The binutils project’s objcopy utility gained an –update-section feature with the 2.26 release. This flag lets you insert the contents of any file into an already existing section in the ELF. You can make use of this flag to do a couple of things that are currently tricky to get right - placing data computed from the contents of the ELF (say the SHA1 hash of flash contents) into a binary, and creating a combined bootloader/application image from two separate binary files.
Read more →
Trying to setup a network server on a ubuntu:vivid docker image, I ran into a weird problem - the server would accept the TCP request and then drop the connection. After eliminating a bunch of possible causes (firewall, SELinux), I found that a simple python TCP server I cooked up worked just fine - it was just that particular network server program that was acting up. It worked perfectly fine on the Arch linux distribution running on my laptop though.
Read more →
Been playing around with docker (http://docker.io) for a while now to see if it can help create a one script setup for setting up the build environment for the avr8 toolchain. One pesky problem when using the device mapper storage driver (the default on RHEL) is that the created images/containers are small - only 10G. That isn’t going to cut it for building the GNU toolchain - the gcc repo itself takes up 2.6G on my machine.
Read more →
If you’re one of the crazy guys building gdb for Windows using the 4.6.1 version of the mingw gcc compiler, here’s something to watch out for. gdb will crash on any error (even a mistyped command), but only on Windows XP. Turns out that gdb uses a setjmp/longjmp based error handling mechanism (see gdb/exceptions.c), and any error causes gdb to execute a longjmp. In Windows land, longjmp is implemented in msvcrt.dll, and it so happens that the implementation expects the frame pointer to be setup correctly.
Read more →
If you’re using GCC’s LTO feature, make sure you repeat the compiler flags when linking. So, if you compile code with -Os -ffunction-sections, make sure you pass the same flags to the gcc driver when linking. This is needed because LTO effectively recompiles by streaming in IR from the object files and regenerating code. Only this time it knows about the code in all the object files that’s going to be part of the final executable, so it can perform a bunch of optimizations it previously couldn’t.
Read more →