forked from minhngoc25a/freetype2
205 lines
7.6 KiB
Plaintext
205 lines
7.6 KiB
Plaintext
Debugging within the FreeType sources
|
|
=====================================
|
|
|
|
I. Configuration macros
|
|
-----------------------
|
|
|
|
There are several ways to enable debugging features in a FreeType 2
|
|
builds. This is controlled through the definition of special macros
|
|
located in the file `ftoption.h'. The macros are:
|
|
|
|
|
|
FT_DEBUG_LEVEL_ERROR
|
|
|
|
#define this macro if you want to compile the FT_ERROR macro calls
|
|
to print error messages during program execution. This will not
|
|
stop the program. Very useful to spot invalid fonts during
|
|
development and to code workarounds for them.
|
|
|
|
FT_DEBUG_LEVEL_TRACE
|
|
|
|
#define this macro if you want to compile both macros FT_ERROR and
|
|
FT_TRACE. This also includes the variants FT_TRACE0, FT_TRACE1,
|
|
FT_TRACE2, ..., FT_TRACE7.
|
|
|
|
The trace macros are used to send debugging messages when an
|
|
appropriate `debug level' is configured at runtime through the
|
|
FT2_DEBUG environment variable (more on this later).
|
|
|
|
FT_DEBUG_MEMORY
|
|
|
|
If this macro is #defined, the FreeType engine is linked with a
|
|
small but effective debugging memory manager that tracks all
|
|
allocations and frees that are performed within the font engine.
|
|
|
|
When the FT2_DEBUG_MEMORY environment variable is defined at
|
|
runtime, a call to FT_Done_FreeType will dump memory statistics,
|
|
including the list of leaked memory blocks with the source
|
|
locations where these were allocated. It is always a very good
|
|
idea to define this in development builds. This works with _any_
|
|
program linked to FreeType, but requires a big deal of memory (the
|
|
debugging memory manager never frees the blocks to the heap in
|
|
order to detect double frees).
|
|
|
|
When FT2_DEBUG_MEMORY isn't defined at runtime, the debugging
|
|
memory manager is ignored, and performance is unaffected.
|
|
|
|
|
|
II. Debugging macros
|
|
--------------------
|
|
|
|
Several macros can be used within the FreeType sources to help
|
|
debugging its code:
|
|
|
|
|
|
1. FT_ERROR(( ... ))
|
|
|
|
This macro is used to send debug messages that indicate relatively
|
|
serious errors (like broken font files), but will not stop the
|
|
execution of the running program. Its code is compiled only when
|
|
either FT_DEBUG_LEVEL_ERROR or FT_DEBUG_LEVEL_TRACE are defined in
|
|
`ftoption.h'.
|
|
|
|
Note that you have to use a printf-like signature, but with double
|
|
parentheses, like in
|
|
|
|
FT_ERROR(( "your %s is not %s\n", "foo", "bar" ));
|
|
|
|
|
|
2. FT_ASSERT( condition )
|
|
|
|
This macro is used to check strong assertions at runtime. If its
|
|
condition isn't TRUE, the program will abort with a panic message.
|
|
Its code is compiled when either FT_DEBUG_LEVEL_ERROR or
|
|
FT_DEBUG_LEVEL_TRACE are defined. You don't need double
|
|
parentheses here. For example
|
|
|
|
FT_ASSERT( ptr != NULL );
|
|
|
|
|
|
3. FT_TRACE( level, (message...) )
|
|
|
|
The FT_TRACE macro is used to send general-purpose debugging
|
|
messages during program execution. This macro uses an *implicit*
|
|
macro named FT_COMPONENT used to name the current FreeType
|
|
component being run.
|
|
|
|
The developer should always define FT_COMPONENT as appropriate,
|
|
for example as in
|
|
|
|
#undef FT_COMPONENT
|
|
#define FT_COMPONENT trace_io
|
|
|
|
The value of the FT_COMPONENT macro is an enumeration named
|
|
`trace_XXXX' where `XXXX' is one of the component names defined in
|
|
the internal file `internal/fttrace.h'. If you modify FreeType
|
|
source and insert new `trace_XXXX' macro, you must register it in
|
|
`fttrace.h'. If you insert or remove many trace macros, you can
|
|
check the undefined or the unused trace macro by
|
|
`src/tools/chktrcmp.py'.
|
|
|
|
Each such component is assigned a `debug level', ranging from 0 to
|
|
7, through the use of the FT2_DEBUG environment variable
|
|
(described below) when a program linked with FreeType starts.
|
|
|
|
When FT_TRACE is called, its level is compared to the one of the
|
|
corresponding component. Messages with trace levels *higher* than
|
|
the corresponding component level are filtered and never printed.
|
|
|
|
This means that trace messages with level 0 are always printed,
|
|
those with level 2 are only printed when the component level is
|
|
*at least* 2.
|
|
|
|
The second parameter to FT_TRACE must contain parentheses and
|
|
correspond to a printf-like call, as in
|
|
|
|
FT_TRACE( 2, ( "your %s is not %s\n", "foo", "bar" ) )
|
|
|
|
The shortcut macros FT_TRACE0, FT_TRACE1, FT_TRACE2, ...,
|
|
FT_TRACE7 can be used with constant level indices, and are much
|
|
cleaner to use, as in
|
|
|
|
FT_TRACE2(( "your %s is not %s\n", "foo", "bar" ));
|
|
|
|
|
|
III. Environment variables
|
|
--------------------------
|
|
|
|
The following environment variables control debugging output and
|
|
behaviour of FreeType at runtime.
|
|
|
|
|
|
FT2_DEBUG
|
|
|
|
This variable is only used when FreeType is built with
|
|
FT_DEBUG_LEVEL_TRACE defined. It contains a list of component
|
|
level definitions, following this format:
|
|
|
|
component1:level1 component2:level2 component3:level3 ...
|
|
|
|
where `componentX' is the name of a tracing component, as defined
|
|
in `fttrace.h', but without the `trace_' prefix. `levelX' is the
|
|
corresponding level to use at runtime.
|
|
|
|
`any' is a special component name that will be interpreted as
|
|
`any/all components'. For example, the following definitions
|
|
|
|
set FT2_DEBUG=any:2 memory:5 io:4 (on Windows)
|
|
export FT2_DEBUG="any:2 memory:5 io:4" (on Linux with bash)
|
|
|
|
both stipulate that all components should have level 2, except for
|
|
the memory and io components which will be set to trace levels 5
|
|
and 4, respectively.
|
|
|
|
|
|
FT2_DEBUG_MEMORY
|
|
|
|
This environment variable, when defined, tells FreeType to use a
|
|
debugging memory manager that will track leaking memory blocks as
|
|
well as other common errors like double frees. It is also capable
|
|
of reporting _where_ the leaking blocks were allocated, which
|
|
considerably saves time when debugging new additions to the
|
|
library.
|
|
|
|
This code is only compiled when FreeType is built with the
|
|
FT_DEBUG_MEMORY macro #defined in `ftoption.h' though, it will be
|
|
ignored in other builds.
|
|
|
|
|
|
FT2_ALLOC_TOTAL_MAX
|
|
|
|
This variable is ignored if FT2_DEBUG_MEMORY is not defined. It
|
|
allows you to specify a maximum heap size for all memory
|
|
allocations performed by FreeType. This is very useful to test
|
|
the robustness of the font engine and programs that use it in
|
|
tight memory conditions.
|
|
|
|
If it is undefined, or if its value is not strictly positive, then
|
|
no allocation bounds are checked at runtime.
|
|
|
|
|
|
FT2_ALLOC_COUNT_MAX
|
|
|
|
This variable is ignored if FT2_DEBUG_MEMORY is not defined. It
|
|
allows you to specify a maximum number of memory allocations
|
|
performed by FreeType before returning the error
|
|
FT_Err_Out_Of_Memory. This is useful for debugging and testing
|
|
the engine's robustness.
|
|
|
|
If it is undefined, or if its value is not strictly positive, then
|
|
no allocation bounds are checked at runtime.
|
|
|
|
------------------------------------------------------------------------
|
|
|
|
Copyright 2002-2017 by
|
|
David Turner, Robert Wilhelm, and Werner Lemberg.
|
|
|
|
This file is part of the FreeType project, and may only be used,
|
|
modified, and distributed under the terms of the FreeType project
|
|
license, LICENSE.TXT. By continuing to use, modify, or distribute this
|
|
file you indicate that you have read the license and understand and
|
|
accept it fully.
|
|
|
|
|
|
--- end of DEBUG ---
|