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Buildroot file system and cross-compilation: a dynamically linked application fails, but a static one is fine. How to link with uClibc

I have a buildroot file system created and I'm trying to execute some c code on a lighttpd server.

I created a simple C module that just prints a few html lines. The code is as follows:

#include "stdio.h" int main(void) { printf( "Content-Type: text/plain\n\n" ); printf("testing C code\n"); return 0; }

I use the compiler from the Ubuntu repository to compile it arm-linux-gnueabi-gcc -o test.cgi test.c If I compiled with the -static flag, it will work fine, and I can see the displayed html. But compilation without a static flag is done like this:

 # ./test.cgi -sh: ./first.cgi: not found

I am wondering if the reason is the wrong c-library, and I should reference the uClibc that compiled by buildroot. In my buildroot folder, output/host/usr/arm-unknown-linux-uclibcgnueabi/sysroot/lib I can see the following files:

 -rwxr-xr-x 1 jlumme jlumme 25444 Jan 26 17:13 ld-uClibc-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 21 Jan 26 17:12 ld-uClibc.so.0 -> ld-uClibc-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 13191 Jan 26 17:13 libcrypt-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 20 Jan 26 17:13 libcrypt.so.0 -> libcrypt-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 21 Jan 26 17:13 libc.so.0 -> libuClibc-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 13383 Jan 26 17:13 libdl-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 17 Jan 26 17:13 libdl.so.0 -> libdl-0.9.33.2.so -rw-r--r-- 1 jlumme jlumme 135 Jan 26 17:15 libgcc_s.so -rw-r--r-- 1 jlumme jlumme 180152 Jan 26 17:15 libgcc_s.so.1 -rwxr-xr-x 1 jlumme jlumme 64555 Jan 26 17:13 libm-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 16 Jan 26 17:13 libm.so.0 -> libm-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 4772 Jan 26 17:13 libnsl-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 18 Jan 26 17:13 libnsl.so.0 -> libnsl-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 79059 Jan 26 17:13 libpthread-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 22 Jan 26 17:13 libpthread.so.0 -> libpthread-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 4776 Jan 26 17:13 libresolv-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 21 Jan 26 17:13 libresolv.so.0 -> libresolv-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 13927 Jan 26 17:13 librt-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 17 Jan 26 17:13 librt.so.0 -> librt-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 284451 Jan 26 17:13 libuClibc-0.9.33.2.so -rwxr-xr-x 1 jlumme jlumme 4955 Jan 26 17:13 libutil-0.9.33.2.so lrwxrwxrwx 1 jlumme jlumme 19 Jan 26 17:13 libutil.so.0 -> libutil-0.9.33.2.so

Is the libuClibc-0.9.33.2.so file I'm looking for? How can I associate my application with this?

In my target board, I see this in /usr/lib

 lrwxrwxrwx 1 root root 15 Jan 26 2013 libbz2.so -> libbz2.so.1.0.6 lrwxrwxrwx 1 root root 15 Jan 26 2013 libbz2.so.1 -> libbz2.so.1.0.6 lrwxrwxrwx 1 root root 15 Jan 26 2013 libbz2.so.1.0 -> libbz2.so.1.0.6 -rwxrwxr-x 1 root root 57924 Jan 26 2013 libbz2.so.1.0.6 lrwxrwxrwx 1 root root 16 Jan 26 2013 libelf.so -> libelf.so.0.8.12 lrwxrwxrwx 1 root root 16 Jan 26 2013 libelf.so.0 -> libelf.so.0.8.12 -rwxr-xr-x 1 root root 69924 Jan 26 2013 libelf.so.0.8.12 lrwxrwxrwx 1 root root 16 Jan 26 2013 libpcre.so -> libpcre.so.1.0.0 lrwxrwxrwx 1 root root 16 Jan 26 2013 libpcre.so.1 -> libpcre.so.1.0.0 -rwxr-xr-x 1 root root 88804 Jan 26 2013 libpcre.so.1.0.0 lrwxrwxrwx 1 root root 19 Jan 26 2013 libpcrecpp.so -> libpcrecpp.so.0.0.0 lrwxrwxrwx 1 root root 19 Jan 26 2013 libpcrecpp.so.0 -> libpcrecpp.so.0.0.0 -rwxr-xr-x 1 root root 27436 Jan 26 2013 libpcrecpp.so.0.0.0 lrwxrwxrwx 1 root root 21 Jan 26 2013 libpcreposix.so -> libpcreposix.so.0.0.0 lrwxrwxrwx 1 root root 21 Jan 26 2013 libpcreposix.so.0 -> libpcreposix.so.0.0.0 -rwxr-xr-x 1 root root 5576 Jan 26 2013 libpcreposix.so.0.0.0 lrwxrwxrwx 1 root root 19 Jan 26 2013 libsqlite3.so -> libsqlite3.so.0.8.6 lrwxrwxrwx 1 root root 19 Jan 26 2013 libsqlite3.so.0 -> libsqlite3.so.0.8.6 -rwxr-xr-x 1 root root 516472 Jan 26 2013 libsqlite3.so.0.8.6 lrwxrwxrwx 1 root root 19 Jan 26 2013 libstdc++.so -> libstdc++.so.6.0.14 lrwxrwxrwx 1 root root 19 Jan 26 2013 libstdc++.so.6 -> libstdc++.so.6.0.14 -rwxr-xr-x 1 root root 418936 Jan 26 2013 libstdc++.so.6.0.14 -rw-r--r-- 1 root root 2422 Jan 26 2013 libstdc++.so.6.0.14-gdb.py lrwxrwxrwx 1 root root 16 Jan 26 2013 libxml2.so -> libxml2.so.2.8.0 lrwxrwxrwx 1 root root 16 Jan 26 2013 libxml2.so.2 -> libxml2.so.2.8.0 -rwxr-xr-x 1 root root 1063556 Jan 26 2013 libxml2.so.2.8.0 drwxrwxr-x 2 root root 4096 Jan 26 2013 lighttpd -rw-r--r-- 1 root root 195 Jan 26 2013 xml2Conf.sh
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To create your application, you need to use the cross-compiler generated by Buildroot located in output/host/usr/bin/<name-of-architecture>-gcc .

Here you are using the Ubuntu ARM cross-compiler, which targets a system that uses the eglibc C library. But the system built using Buildroot uses the uClibc C library. Thus, there is no way for a binary file built into the Ubuntu ARM cross-compiler to work on this generated Buildroot system.

Just use the Buildroot cross compiler for you.

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Source: https://habr.com/ru/post/971859/

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