[Libreoffice] Assertions and Logging

[Stephan Bergmann]

I pushed the proposed changes as 
<http://cgit.freedesktop.org/libreoffice/core/commit/?id=70a6b9ffbd676a1384433a86205d2cd4f2d4f4b1> 
and 
<http://cgit.freedesktop.org/libreoffice/binfilter/commit/?id=d45d5ee81e3d3f1779774af3f400ce3f1aa6697d>. 
  Any further refinements (where to send the log output, performance 
considerations) can carry on from there.

I added a short summary as 
<https://wiki.documentfoundation.org/Development#Assertions_and_Logging>; feel 
free to expand.  I also filed easy hack 
<https://bugs.freedesktop.org/show_bug.cgi?id=43157> "Clean up 
OSL_ASSERT, DBG_ASSERT, etc."  As already discussed, if any uses of the 
obsolete functionality still remains after a while, I would initiate a 
mass-conversion OSL_ASSERT->SAL_WARN, OSL_TRACE->SAL_INFO, etc.

I made a few further changes to the proposed patches when I pushed them:

- DBG_ASSERT etc. from tools/debug.hxx still are only enabled depending 
on DBG_UTIL.  Trying an --enable-debug --disable-dbgutil build, it broke 
at many places that #ifdef DBG_UTIL some code that is later used within 
a DBG_ASSERT (e.g., an additional variable capturing some old value, 
modified later and checked afterwards, or a function parameter name that 
is only used within a DBG_ASSERT).  This is a lot of work to clean up 
(see the easy hack above).

- I replaced the single SAL_LOG_LEVEL (with values 0, 1, 2) with 
individual defines SAL_LOG_INFO and SAL_LOG_WARN.  This makes it easier 
to replace the code mentioned above, going from

   #ifdef DBG_UTIL
     int old = x;
   #endif
     ... // modify x
     DBG_ASSERT(x > old);

to

   #if defined SAL_LOG_WARN // instead of: SAL_LOG_LEVEL >= 1
     int old = x;
   #endif
     .. // modify x
     SAL_WARN_IF(x <= old, "...");

(Where for such a cheap initialization like "int old = x;" it would also 
work to have that variable included unconditionally, followed by a 
"(void) old; // avoid warnings"; but there are also cases of more 
expensive initialization, that you would likely want to keep excluded 
from production builds.)

- The SAL_INFO/WARN messages are now defined to be always UTF-8, and 
rtl/oustringostreaminserter.hxx always converts to UTF-8.  That 
minimizes information loss and would potentially enable use of 
SAL_STREAM for construction of UNO exception messages, see the recent 
thread about that.  However, I do not bother to convert the data output 
to stderr from UTF-8 to any other encoding.

Stephan