It appears that include file is from new version while actually compiled with old version.

Reproduced.

Prerequisites

2 libraries installed:

/usr/lib/x86_64-linux-gnu/libcurl.so (7.64.0)
/usr/local/lib/libcurl.so            (8.5.0)

There is a libcurl function Zabbix needs: curl_easy_header, introduced in cURL 7.83.0 (as you can see, not available in older installed version).

What happens

That's a linker error, not a compiler, so the header file is not an issue. What seems to be an issue is the order of -L options passed to the linker. And this order depends on the features enabled when running ./configure .

I was able to reproduce the issue when configuring Zabbix server with MySQL:

$ ./configure --enable-server --with-mysql --with-libcurl=/usr/local/bin/curl-config
[...]
Linker flags:                -L/usr/lib/x86_64-linux-gnu/ -L/usr/local/lib -rdynamic

Running make, you get the linker error (note the order of -L options):

cc <OPTS> -L/usr/lib/x86_64-linux-gnu/ -L/usr/local/lib <OPTS>
/usr/bin/ld: ../../src/libs/zbxhttp/libzbxhttp.a(http.o): in function `zbx_http_convert_to_utf8':
/root/git/zabbix-master/src/libs/zbxhttp/http.c:957: undefined reference to `curl_easy_header'
collect2: error: ld returned 1 exit status 

This is because it will find the "old" curl library in

/usr/lib/x86_64-linux-gnu/libcurl.so 

which doesn't have the required function.

Why is /usr/lib/x86_64-linux-gnu/ listed first?

This is because in ./configure we first check for MySQL things:

$ mariadb_config --libs  
-L/usr/lib/x86_64-linux-gnu/ -lmariadb 

remember those and later, the libcurl things:

$ /usr/local/bin/curl-config --libs  
-L/usr/local/lib -lcurl

which results in the following string:

-L/usr/lib/x86_64-linux-gnu/ -L/usr/local/lib

If we just build the agent, it's all good, because we don't get that first part from MySQL config and correct cURL library is used (/usr/local/lib/libcurl.so):

$ ./configure --enable-agent --with-libcurl=/usr/local/bin/curl-config
[...]
Linker flags:                -L/usr/local/lib -rdynamic

$ make
[...]

$ echo $?
0

Have a look to ZBX-23861.

Solution 1

The simplest solution is to specify the path to the desired library to use manually in LDFLAGS:

$ LDFLAGS="/usr/local/lib/libcurl.so" ./configure --enable-server --with-mysql --with-libcurl=/usr/local/bin/curl-config

Solution 2

More complex solution would require to rewrite the way we work with pkg-config and generate direct path to the libraries instead of using a combination of -L<dir> and -l<lib>. E. g. if <pkg-config utility> --libs returns

-L/usr/local/lib -lcurl

translate this to

/usr/local/lib/libcurl.so

Solution 3

Tell user to remove the older library installed in standard path.

I vote for Solution #1. User still has control over compilation process even in this corner case. Perhaps we could even document this.

Was decided with sasha to go for #1 and document the workaround.

It appears that there is a possibility that user might be unaware that Zabbix gets compiled with older library even when asked to use the newer one.

Let's document the workaround but keep this one open until proper solution.

Follow up on documentation: ZBX-23873

This workaround:

LDFLAGS="/usr/local/lib/libcurl.so" ./configure --enable-server --with-mysql --with-libcurl=/usr/local/bin/curl-config

may not work because LDFLAGS are placed before the list of server files and libraries.

This one works:

LIBCURL_LIBS="/usr/local/lib/libcurl.so" ./configure --enable-server --with-mysql --with-libcurl=/usr/local/bin/curl-config

Because it disables curl-config --libs logic in configure and injects the library directly into the right place.

<dimir> I have checked the cc command that links zabbix_server binary and it's absolutely identical in my and your cases. Though, it works in my case but fails in yours.

But your version also works in my case. Looks like it's more reliable as it completely overrides LIBCURL_LIBS:

Proposed workaround

$ LDFLAGS="-Wl,--no-as-needed /usr/local/lib/libcurl.so" ./configure --enable-server --with-mysql --with-libcurl=/usr/local/bin/curl-config

will be documented in ZBX-23873