Sqlite load extension disabled?

Question

I'm trying to use this sqlite extension to calculate stdev in Sqlite dbs, on Linux, I use this command to compile the lib

gcc -fPIC -lm -shared extension-functions.c -o libsqlitefunctions.so

but seems that the .load command is not in the sqlite .help command list, and I got error:

unknown command or invalid arguments: "load". Enter ".help" for help

Same thing happens when I use the command:

 sqlite> SELECT load_extension('./libsqlitefunctions.so');

SQL error: no such function: load_extension

I tried to use this instruction to compile sqlite:

0. untar latest sqlite3 source code in a new directory

1. cd to the newly untarred sqlite directory

2. Comment out the line in Makefile.in to enable loadable extensions:

     # TCC += -DSQLITE_OMIT_LOAD_EXTENSION=1

3. ./configure LIBS=-ldl && make sqlite3

4. export LD_LIBRARY_PATH="`pwd`:$LD_LIBRARY_PATH"

5. gcc -I`pwd` -shared src/test_loadext.c -o half.so

6. ./sqlite3

But couldn't find the line "TCC += -DSQLITE_OMIT_LOAD_EXTENSION=1" in the newest Sqlite source code.

Answer 1

It looks like configure was updated but not the documentation. Try

./configure --enable-dynamic-extensions

The reference is the configure source code. Digging further, it looks like the dynamic extensions are enabled by default. From README:

The generic installation instructions for autoconf/automake are found  
in the INSTALL file.

The following SQLite specific boolean options are supported:

  --enable-readline           use readline in shell tool   [default=yes]
  --enable-threadsafe         build a thread-safe library  [default=yes]
  --enable-dynamic-extensions support loadable extensions  [default=yes]

So I think load is present. It's the second part of the error invalid arguments that's the problem.

The cause seems to be that you're using Linux instructions. That won't work. Macs don't generally have .so files, which is what your compilation command is generating.

The method of compiling and loading a Mac dynamic library, loadable as an extension, is at this location. The compile command is going to look something like

gcc -bundle -fPIC -I/path-to-sqlite/sqlite3 -o filename.sqlext filename.c

Note the -bundle and -fPIC that are important for dynamic loading, but which you were missing. The resulting filename will be filename.sqlext, so use that in your path.

Answer 2

It may be worth noting that you may get a "missing symbols" error when you load the library - this is due to the fact that the -lm flag needs to be at the end of the compile command thus:

gcc -fPIC -shared extension-functions.c -o libsqlitefunctions.so -lm

Regards Fat jonnie