Ntopng fails to build on gentoo with gcc 13.2 invalid conversion from 'char**' to 'const char**'

[adippl]

Environment:

• OS name: Gentoo
• OS version: current
• Architecture: amd64
• ntopng version/revision: 5.6

What happened:
Ntopng fails to build on gentoo with gcc 13.2.1_p20240113-r1::gentoo

src/LuaEngineNtop.cpp: In function 'int ntop_rrd_tune(lua_State*)':
src/LuaEngineNtop.cpp:5709:27: error: invalid conversion from 'char**' to 'const char**' [-fpermissive]
 5709 |   status = rrd_tune(argc, (char**)argv);
      |                           ^~~~~~~~~~~~
      |                           |
      |                           char**
In file included from src/LuaEngineNtop.cpp:25:

How did you reproduce it?
Package doesn't compile for me and other users.

Link to gentoo buzilla bug with patch solving this issue.
https://bugs.gentoo.org/861230

[lucaderi]

I'm sorry, we won't be able to accept your fix because you are not using the same RRD library we are using. If you look at https://github.com/ntop/ntopng/blob/dev/third-party/rrdtool-1.4.8/src/rrd.h#L204 if we accept your patch we'll break our code.

[adippl]

Does ntopng officially supports only old rrdtool version 1.4.8 or is this a library fork?
Are there technical reasons for it?
A lot of other distributions like ubuntu, arch or debian ship significantly newer version of this library.

[eli-schwartz]

I'm sorry, we won't be able to accept your fix because you are not using the same RRD library we are using. If you look at https://github.com/ntop/ntopng/blob/dev/third-party/rrdtool-1.4.8/src/rrd.h#L204 if we accept your patch we'll break our code.

Please apply a patch that does work, then.

This should not be too complicated: Makefile.in checks for HAS_LIBRRDTOOL via pkg-config and in the absence of a pkg-config detected system copy it uses the included copy.

That check can set a -DHAS_LIBRRDTOOL which can then be used to conditionalize the patch logic to only apply on versions of rrdtool where it is relevant.

@adippl can you update the patch to do so and submit a PR?

[adippl]

@eli-schwartz I'm not super familiar with these build systems and cannot get this to work.
Could you create patch with this solution?

If I'm reading makefile.in correctly build system should auto build rrdtool-1.4.8 if system one isn't available.
I've tried to build this way but ntopng's rrdtool-1.4.8 failed to build on my system.

ntopng/Makefile.in

Line 49 in e7f302e

HAS_LIBRRDTOOL=$(shell $(PKG_CONFIG) --atleast-version=1.4.8 librrd && echo 0)

Also, It would be good idea to change pkg-config rrdtool version detection to --exact-version=1.4.8 since if officially supports only this version.