Set custom library path to execute a CGI file from the uhttpd

Question

I am working on OpenWrt 23.05, to run a CGI script from the browser URL e.g. http://192.168.1.1/cgi-bin/myapp.cgi The server is uHTTPd. My CGI file is written in C++ that needs no interpreter. The CGI file depends on some libraries that are present in /opt/lib/ folder and not in the /usr/lib folder.

In the CGI makefile added the rpath -Wl, rpath=/opt/lib/. With this change, the CGI runs and passes all the cases when the binary is copied to the target device (/www/cgi-bin) folder. However when I install the .ipk or copy the CGI file present in the .ipk file, it doesn't work. Looks like the symbols and RPATH are stripped from the ipk binary.

I have tried the following as suggested by ChatGPT/Gemini but none working.

Added the "PKG_BUILD_FLAGS := no-strip" in the openwrt makefile and not working.
Added the option cgi_env 'LD_LIBRARY_PATH=/opt/lib' - I doubt it is a valid uHTTPd UCI setting

Here is the error snippet,

export LD_LIBRARY_PATH=
~ # ldd /www/cgi-bin/myapp.cgi
        libpcre.so.1 => /usr/lib/libpcre.so.1 (0x7f99f29000)
        libpcrecpp.so.0 => /usr/lib/libpcrecpp.so.0 (0x7f99f08000)
        libsqlite3.so.0 => /usr/lib/libsqlite3.so.0 (0x7f99d43000)
        libcgicc.so.3 => /usr/lib/libcgicc.so.3 (0x7f99d12000)
        libctpp2.so.2 => /usr/lib/libctpp2.so.2 (0x7f99c71000)
Error loading shared library libmgr.so: No such file or directory (needed by /www/cgi-bin/myapp.cgi)

libmgr.so - is my custom library present in /opt/lib

It also suggest to run the CGI file inside a script (.sh) file and provide the library path before execution. I believe it works but I don't want a script in-between.

Any suggestions in fixing this?

Nick ODell · Accepted Answer · 2025-07-24 19:29:37Z

0

Here's what I would suggest to make the LD_LIBRARY_PATH change permanent on OpenWRT.

Edit /etc/ld.so.conf. Add a line to it, with the path of the directory holding the library.

/opt/lib
Run ldconfig as root. This will re-build the /etc/ld.so.cache file, which should add your new file to the index.
If you need to add more files to the /opt/lib directory, you will need to re-run ldconfig.

Source: The "Setup library search paths using ld.so.conf" section of this page from the OpenWRT wiki.

Note: I have not tested the preceding suggestion.

answered Jul 24 at 19:29

Nick ODell

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