Platform Limitations

Many people today are using 64-bit platforms like the MacBook Pro, with an Intel i7 processor or similar. This may present a problem if you want to build a cross-compiler for the Raspberry Pi, which is a 32-bit platform. The 32-bit cross-compiler must be built on a 32-bit processor.

If you are using a 64-bit platform, then you’ll probably want to choose a VirtualBox solution or use an older Linux 32-bit server. This gives you a 32-bit operating system to host the cross-compiler on. On the other hand, if you are already running a 32-bit operating system, creating a native cross-compiler should be a slam dunk.

Without VirtualBox (Native)

Using VirtualBox (Debian/Linux)

If you do not have a suitable Linux environment, one can be hosted on the platform you have. You can host Linux from Windows, Mac OS X, Solaris, or another distribution of Linux using VirtualBox downloaded from the following:

www.virtualbox.org

Download crosstool-NG

The released crosstool-NG downloads are found at:

http://crosstool-ng.org

Staging Directory

Unpack the Tarball

After the unpacking completes, you should have a subdirectory named crosstoolng-1.23.0 in your staging directory.

Create /opt/x-tools

Optionally, once the installation is complete later, you can change the ownership back to root for protection.

Install Package Dependencies

If during the configuration of crosstools-ng you find that you need other packages, they can be installed then and the configuration retried.

Configure crosstools-NG

If this completes without errors, you are ready to build and install the software. If it reports that you are missing package dependencies, install them now and repeat.

Patch inputbox.c

One extremely vexing irritation I have with some modern Linux and tools, is that they don't properly support the backspace character (Control-H). This is a standard ASCII character intended precisely for this purpose. Why has it been banished? I'll try to refrain from further ranting about this.

The menu program used by the crosstool-ng suffers from the same problem that the linux kernel menuconfig suffers from: no backspace character (Control-H) support. This can leave you in the curse-worthy situation of not being able to backspace or delete input.

If you already know that your backspace key sends an escape sequence instead of Control-H, then you can safely skip this change. Otherwise, this kind of thing can drive you absolutely batty. With that file saved, some semblance of sanity will follow.

make crosstool-ng

This takes very little time and seems trouble free.

make install

If you still own the directory /opt/x-tools from earlier (recall sudo chown fred /opt/x-tools), you won’t need to use sudo in the preceding step. After make install is performed, you will have the crosstool-NG command ct-ng installed in the directory /opt/x-tools/bin.

PATH

Paths and Misc Options

When the ct-ng command starts up, the menu configuration screen is presented as shown in Figure 20-1. Press Enter to open the Paths and Misc Options submenu.

Once in the Paths and Misc Options menu, as shown in Figure 20-2, use the cursor key to move down to Try Features Marked as Experimental. Once that line is highlighted, press the spacebar to put an asterisk inside the square brackets to select the option (pressing space again toggles the setting).

After doing that, while in the same menu, move the cursor down to the middle entry labeled Prefix Directory and press Enter to select it (Figure 20-3). Unfortunately, recent defaults prevent you from seeing the “Prefix Directory” text at the extreme right of the menu selection.

Figure 20-4 illustrates the input dialog. If you find that you cannot use backspace, then apply the fix discussed in section “Patch inputbox.c”.

Once the pathname is established, press Enter on the OK button shown. This returns you to the Paths and Misc Options menu.

Then select the Exit button shown at the bottom, and press Enter again. If you have changed anything that needs saving then choose “Yes” (Figure 20-5).

Target Options

Restart the menu and select Target Options with the cursor and press Enter to open it (Figure 20-6).

Then choose Target Architecture and press Enter (Figure 20-7).

In that menu, choose arm and press space (Figure 20-8). Then use the Select button at the bottom. This returns you to the Target Options menu.

While in the Target Options menu (shown next), verify the Endianness setting by reviewing the status in round brackets. It should read Little Endian (Figure 20-9). If not, enter that menu and change it to Little endian. Below the Endianness menu item is the Bitness option. It should already indicate 32-bit. If not, change it.

Finally, exit this submenu with the Exit button.

Operating System

At the main menu again (Figure 20-10), choose Operating System and then choose Target OS (bare-metal) as shown in Figure 20-11.

Once you have chosen “linux” in Figure 20-12, exit back to the main menu.

Binary Utilities

At the main menu, open the Binary Utilities menu (Figure 20-13).

Cursor down to Binutils Version and open it (Figure 20-14).

Once into the final binutils version selection menu, pick the most recent version unless you experienced trouble with a prior build attempt (Figure 20-15).

Exit back to the main menu.

C Compiler

At the main menu, open the C Compiler submenu (Figure 20-16).

Here it is recommended that you enable the Show Linaro Versions option (Figure 20-17).

Once that is enabled, you can select the submenu Gcc Version (Figure 20-18).

Figure 20-19 shows a recent version of the Linaro compiler being chosen.

Then choose Exit once again to return to the main menu.

Save Configuration

Unless you have a reason to change anything else, exit the menu again to cause the Save prompt to appear:

Saving the file outside the current directory will prevent accidental loss if ct-ng distclean is used.

Troubleshooting

Using less, you can navigate to the end of the build.log file by typing a capital G.

One failure that frequently occurs in the beginning is a failed download. While the build process does retry downloads and tries different download methods, it can still fail. All that you need to do is to retry the build. It will download only the remaining files needed. Sometimes it will succeed on the second or third retry attempt.

Navigate to the end of config.log and work backward a few pages. Eventually, you will see text describing the command that was tried and the error message produced. In one instance, I was able to determine that the custom compiler option that I added (-fpermissive) was causing the failure. The solution then was to remove that option and try again.

Some errors will only occur with certain version choices. At one time, I was receiving errors related to PPL and needed a patch to correct it.

In getting through these issues, you can simply make corrections and then rerun the ct-ng build command. It is recommended that you plan for a later rebuild of everything again (after a clean), once the problems are solved. This will ensure that you have a good build without dependency issues.

The ct-ng clean command will usually be enough, forcing the next build to start fresh. Any downloaded files and configuration will remain and will be reused.

The ct-ng distclean command is much more drastic, since it removes all of the downloaded content and your configuration files. I had copied the .config file to .config.bak and discovered to my horror that .config.bak had also been removed! So if you back up the .config file, copy it outside the current directory for safety.

Above all, keep your head. It’s difficult to troubleshoot these issues if you feel time pressure or get angry over the time invested. When under time pressure, leave it for another day when you can deal with it thoughtfully. Each redo takes considerable time. Wherever possible, eliminate the guesswork.

With each problem, take a deep breath, patiently look for clues, and pay attention to the details in the error messages. Remember that line in the movie Apollo 13: “Work the problem, people!”