filled-in text in the "Building" chapter and added a "libcurl with C++"

chapter

docs/libcurl-the-guide

@@ -10,7 +10,7 @@ PROGRAMMING WITH LIBCURL
 About this Document
 
  This document will attempt to describe the general principle and some basic
- approach to consider when programming with libcurl. The text will focus
+ approaches to consider when programming with libcurl. The text will focus
  mainly on the C/C++ interface but might apply fairly well on other interfaces
  as well as they usually follow the C one pretty closely.
 
@@ -23,12 +23,44 @@ About this Document
 
 Building
 
+  There are many different ways to build C programs. This chapter will assume
+  a unix-style build process
+
   Compiling the Program
 
+    Your compiler needs to know where the libcurl headers are
+    located. Therefore you must set your compiler's include path to point to
+    the directory where you installed them. The 'curl-config' tool can be used
+    to get this information:
+
+        $ curl-config --cflags
+
   Linking the Program with libcurl
 
+    When having compiled the program, you need to link your object files to
+    create a single executable. For that to succeed, you need to link with
+    libcurl and possibly also with other libraries that libcurl itself depends
+    on. Like OpenSSL librararies, but even some standard OS libraries may be
+    needed on the command line. To figure out which flags to use, once again
+    the 'curl-config' tool comes to the rescue:
+
+        $ curl-config --libs
+
   SSL or Not
 
+    libcurl can be built and customized in many ways. One of the things that
+    varies from different libraries and builds is the support for SSL-based
+    transfers, like HTTPS and FTPS. If OpenSSL was detected properly at
+    build-time, libcurl will be built with SSL support. To figure out if an
+    installed libcurl has been built with SSL support enabled, use
+    'curl-config' like this:
+
+        $ curl-config --feature
+
+    And if SSL is supported, the keyword 'SSL' will be written to stdout,
+    possibly together with a few other features that can be on and off on
+    different libcurls.
+
 
 Global Preparation
 
@@ -199,6 +231,27 @@ Upload Data to a Remote Site
  fast as possible. The callback should return the number of bytes it wrote in
  the buffer. Returning 0 will signal the end of the upload.
 
+libcurl with C++
+
+ There's basicly only one thing to keep in mind when using C++ instead of C
+ when interfacing libcurl:
+
+    "The Callbacks Must Be Plain C"
+
+ So if you want a write callback set in libcurl, you should put it within
+ 'extern'. Similar to this:
+
+     extern "C" {
+       size_t write_data(void *ptr, size_t size, size_t nmemb,
+                         void *ourpointer)
+       {
+         /* do what you want with the data */
+       }
+    }
+
+ This will of course effectively turn the callback code into C. There won't be
+ any "this" pointer available etc.
+
 
 -----
 Footnotes: