curl: use dynbuf for config file buffer management

[bagder]

By making the dynbuf functions available as curlx_ verisons, the config file parser in the tool code can use that for its buffer management and for saver reallocs etc.

Once landed, we can move more curl functions over to dynbuf,

(Alternative take to #5941 )

[jay]

Sharing memory allocation functions between the tool and library is tricky. In Windows the tool and library can each be using a separate CRT if libcurl is a DLL and therefore have separate memory handling. Also it would probably be slower to call into the DLL for each dynbuf memory call.

[bagder]

Yes, but this isn't meant to share allocation functions. It is meant to share the dynbuf.c code and the allocations done by the tool should be done like normal tool-side allocations. Still a bit tricky to get right in the build systems but I think I'm almost there now...

[jay]

If the code is built separately for the tool and library and there's naming conflicts and the tool and library can't both use the same function name (I seem to remember that's happened before) then you could change the function name depending on BUILDING_LIBCURL like

#ifdef BUILDING_LIBCURL
#define DYN_FNAME(x) libcurl_ ## x
#else
#define DYN_FNAME(x) x
#endif

void DYN_FNAME(dyn_nappend) (...

[bagder]

Ah right, it will be a problem in static builds...

[bagder]

I opted to plain redefined function names for the tool. I think it looks and feels better.

[bagder]

Can anyone figure out why the visual studio project build fails?

tool_parsecfg.obj : error LNK2019: unresolved external symbol curlx_dyn_init referenced in function parseconfig
tool_parsecfg.obj : error LNK2019: unresolved external symbol curlx_dyn_free referenced in function parseconfig
tool_parsecfg.obj : error LNK2019: unresolved external symbol curlx_dyn_add referenced in function my_get_line
tool_parsecfg.obj : error LNK2019: unresolved external symbol curlx_dyn_reset referenced in function parseconfig
tool_parsecfg.obj : error LNK2019: unresolved external symbol curlx_dyn_ptr referenced in function parseconfig

1. It was winbuild, not visual studio
2. I figured it out

[bagder]

This looks fine now and I'll land this (unless someone objects) within a day or two.

[bagder]

Yet another force-push

[bagder]

Okay, pushed a new version that makes curl actually return an error back out if it runs into an out of memory.

[bagder]

If you are only having a single line in the buffer at any time then that is not necessary you could just reset it.

This logic is doing exactly one line at a time...

[Jan-E]

The fix for this seems to break the standard commandline that the PHP devs use: winlibs/cURL#16