ref: d355a73aa3821ae83e0e28e0888eb22dd83b2d96
parent: 1f4e5bcb19eaa9170466c8d845edfd11aba54937
author: Werner Lemberg <wl@gnu.org>
date: Sun Oct 6 16:07:09 EDT 2019
docs/DEBUG: Document environment variable `FT2_KEEP_ALIVE'. Also do some formatting and minor edits.
--- a/docs/DEBUG
+++ b/docs/DEBUG
@@ -11,20 +11,20 @@
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
+ #define this macro if you want to compile the `FT_ERROR' macro
+ calls to print error messages during program execution. This does
+ 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.
+ #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).
+ `FT2_DEBUG' environment variable (more on this later).
FT_DEBUG_MEMORY
@@ -32,16 +32,16 @@
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 the `FT2_DEBUG_MEMORY' environment variable is defined at
+ runtime, a call to `FT_Done_FreeType' dumps memory statistics,
+ including the list of leaked memory blocks and optionally 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
+ When `FT2_DEBUG_MEMORY' isn't defined at runtime, the debugging
memory manager is ignored, and performance is unaffected.
@@ -55,10 +55,10 @@
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
+ serious errors (like broken font files) without stopping 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'.
+ 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
@@ -69,10 +69,10 @@
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
+ condition isn't TRUE, the program aborts 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. Example:
FT_ASSERT( ptr != NULL );
@@ -79,43 +79,43 @@
3. FT_TRACE( level, (message...) )
- The FT_TRACE macro is used to send general-purpose debugging
+ 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
+ macro named `FT_COMPONENT', which names the current FreeType
component being run.
- The developer should always define FT_COMPONENT as appropriate,
+ The developer should always define `FT_COMPONENT' as appropriate,
for example as in
#undef FT_COMPONENT
#define FT_COMPONENT io
- The value of the FT_COMPONENT macro is one of the component
- names defined in the internal file `internal/fttrace.h'. If you
- modify FreeType source and insert new FT_COMPONENT 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'.
+ The value of the `FT_COMPONENT' macro is one of the component
+ names defined in the internal file `internal/fttrace.h'. If you
+ modify the FreeType source code and insert a new `FT_COMPONENT'
+ macro, you must register it in `fttrace.h'. If you insert or
+ remove many trace macros, you can test for undefined or unused
+ trace macros with the script `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.
+ Each such component is assigned a `debug level', ranging from
+ value 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
+ 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.
+ the corresponding component level are filtered out 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, etc.
- 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
+ corresponds to a printf-like call, as in
- 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
+ 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" ));
@@ -131,7 +131,7 @@
FT2_DEBUG
This variable is only used when FreeType is built with
- FT_DEBUG_LEVEL_TRACE defined. It contains a list of component
+ `FT_DEBUG_LEVEL_TRACE' defined. It contains a list of component
level definitions, following this format:
component1:level1 component2:level2 component3:level3 ...
@@ -140,14 +140,14 @@
in `fttrace.h'. `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
+ `any' is a special component name that is 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
+ the memory and io components, which are set to the trace levels 5
and 4, respectively.
@@ -154,39 +154,52 @@
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
+ debugging memory manager that tracks 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
+ `FT_DEBUG_MEMORY' macro #defined in `ftoption.h' though, it is
ignored in other builds.
FT2_ALLOC_TOTAL_MAX
- This variable is ignored if FT2_DEBUG_MEMORY is not defined. It
+ 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.
+ If it is undefined, or if its value is not strictly positive, no
+ allocation bounds are checked at runtime.
FT2_ALLOC_COUNT_MAX
- This variable is ignored if FT2_DEBUG_MEMORY is not defined. It
+ 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
+ `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.
+ If it is undefined, or if its value is not strictly positive, no
+ allocation bounds are checked at runtime.
+
+
+ FT2_KEEP_ALIVE
+
+ This variable is ignored if `FT2_DEBUG_MEMORY' is not defined.
+ `Keep alive' means that freed blocks aren't released to the heap.
+ This is useful to detect double-frees or weird heap corruption,
+ reporting the source code location of the original allocation and
+ deallocation in case of a problem. It uses large amounts of
+ memory, however.
+
+ If it is undefined, or if its value is not strictly positive,
+ freed blocks are released at runtime.
------------------------------------------------------------------------