Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about how to compile SQLite. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

Last week, I was working on a SQL website. I use sqlite to run all the queries on the site, and I want to use window functions in one of the examples (this).

But I'm using the sqlite version of Ubuntu 18.04, which is too old to support window functions. So I need to upgrade sqlite!

As it turns out, this process is very troublesome (as usual), but very interesting! I think of some information about how executables and shared libraries work, and the results are satisfactory. So I want to write it down here.

Try 1: download the SQLite binaries from its website

The download page of SQLite has a link to the binaries of the SQLite command-line tool for Linux. I downloaded it, it could run on my laptop, and I thought it was done.

But then I tried to run it on the build server (Netlify) and got this extremely strange error message: "File not found". I tracked it and determined that execve returned the error code ENOENT, which means "File not found". This is a little crazy because the file does exist and has the correct permissions.

I searched this question (by searching for "execve enoen") and found the answer in this stackoverflow, which points out that to run binaries, you not only need binaries to exist! You also need its loader to exist. (the path of the loader is inside the binary file)

To see the path to the loader, you can use ldd, as follows:

$ldd sqlite3 linux-gate.so.1 (0xf7f9d000) libdl.so.2 = > / lib/i386-linux-gnu/libdl.so.2 (0xf7f70000) libm.so.6 = > / lib/i386-linux-gnu/libm.so.6 (0xf7e6e000) libz.so.1 = > / lib/i386-linux-gnu/libz.so.1 (0xf7e4f000) libc.so.6 = > / lib/i386-linux-gnu/libc.so.6 (0xf7c73000) / lib/ld-linux.so.2

So / lib/ld-linux.so.2 is a loader, and the file does not exist on the build server, probably because Xenial (Xenial is Ubuntu 16.04, this article should use 18.04 "Bionic Beaver") the installer does not support 32-bit binaries (? So I need to try something different.

Try 2: install the Debian sqlite3 package

Well, I think I might be able to install the sqlite package from debian testing. It's not a good idea to try to install a package from another version of Debian that I don't use, but for some reason I decided to give it a try.

This unsurprisingly broke the sqlite on my computer (which also destroyed git), but I managed to recover through sudo dpkg-- purge-- force-all libsqlite3-0 and make all the software that depends on sqlite work again.

Try 3: extract the Debian sqlite3 package

I also tried to extract the sqlite3 binaries only from the Debian sqlite package and run it. Not surprisingly, this doesn't work, but this is easier to understand: I have an older version of libreadline (.so.7), but it requires .so.8.

$. / usr/bin/sqlite3./usr/bin/sqlite3: error while loading shared libraries: libreadline.so.8: cannot open shared object file: No such file or directory try 4: compile from source code

The reason I spend so much time trying to download sqlite binaries is that I think compiling sqlite from source code is annoying and time-consuming. But obviously, downloading any sqlite binary is not for me at all, so I finally decided to try to compile it myself.

Here's a guide: how to compile SQLite. It's the simplest thing in the universe. In general, the feeling of compilation is something like this:

Run. / configure

I realized my lack of dependence.

Run. / configure again

Run make

Compilation failed because I installed the wrong version of the dependency

To do something else, and then find the binaries.

SQLite is compiled in the following way:

Download the integrated tarball from the download page

Run gcc shell.c sqlite3.c-lpthread-ldl

Done!

All the code is in one file (sqlite.c), and there are no strange dependencies! Fantastic.

For me, I don't really need thread support or readline support, so I used the instructions on the compilation page to create a very simple binary that uses only libc and no other shared libraries.

$ldd sqlite3 linux-vdso.so.1 (0x00007ffe8e7e9000) libc.so.6 = > / lib/x86_64-linux-gnu/libc.so.6 (0x00007fbea4988000) / lib64/ld-linux-x86-64.so.2 (0x00007fbea4d79000) this is good because it makes it easy to experience sqlite

I think it's cool to build SQLite so easily, because I used to be happy to edit the source code of sqlite to understand how its B-tree is implemented.

Given what I know about SQLite, this is not surprising (it does work well in a restricted environment / embedded, so it makes sense to compile in a very simple / minimal way).

The above is the editor for you to share how to compile SQLite, if you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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