1 Debugging within the FreeType sources |
|
2 ===================================== |
|
3 |
|
4 I. Configuration macros |
|
5 ----------------------- |
|
6 |
|
7 There are several ways to enable debugging features in a FreeType 2 |
|
8 builds. This is controlled through the definition of special macros |
|
9 located in the file `ftoptions.h'. The macros are: |
|
10 |
|
11 |
|
12 FT_DEBUG_LEVEL_ERROR |
|
13 |
|
14 #define this macro if you want to compile the FT_ERROR macro calls |
|
15 to print error messages during program execution. This will not |
|
16 stop the program. Very useful to spot invalid fonts during |
|
17 development and to code workarounds for them. |
|
18 |
|
19 FT_DEBUG_LEVEL_TRACE |
|
20 |
|
21 #define this macro if you want to compile both macros FT_ERROR and |
|
22 FT_TRACE. This also includes the variants FT_TRACE0, FT_TRACE1, |
|
23 FT_TRACE2, ..., FT_TRACE7. |
|
24 |
|
25 The trace macros are used to send debugging messages when an |
|
26 appropriate `debug level' is configured at runtime through the |
|
27 FT2_DEBUG environment variable (more on this later). |
|
28 |
|
29 FT_DEBUG_MEMORY |
|
30 |
|
31 If this macro is #defined, the FreeType engine is linked with a |
|
32 small but effective debugging memory manager that tracks all |
|
33 allocations and frees that are performed within the font engine. |
|
34 |
|
35 When the FT2_DEBUG_MEMORY environment variable is defined at |
|
36 runtime, a call to FT_Done_FreeType will dump memory statistics, |
|
37 including the list of leaked memory blocks with the source locations |
|
38 where these were allocated. It is always a very good idea to define |
|
39 this in development builds. This works with _any_ program linked to |
|
40 FreeType, but requires a big deal of memory (the debugging memory |
|
41 manager never frees the blocks to the heap in order to detect double |
|
42 frees). |
|
43 |
|
44 When FT2_DEBUG_MEMORY isn't defined at runtime, the debugging memory |
|
45 manager is ignored, and performance is unaffected. |
|
46 |
|
47 |
|
48 II. Debugging macros |
|
49 -------------------- |
|
50 |
|
51 Several macros can be used within the FreeType sources to help debugging |
|
52 its code: |
|
53 |
|
54 |
|
55 1. FT_ERROR(( ... )) |
|
56 |
|
57 This macro is used to send debug messages that indicate relatively |
|
58 serious errors (like broken font files), but will not stop the |
|
59 execution of the running program. Its code is compiled only when |
|
60 either FT_DEBUG_LEVEL_ERROR or FT_DEBUG_LEVEL_TRACE are defined in |
|
61 `ftoption.h'. |
|
62 |
|
63 Note that you have to use a printf-like signature, but with double |
|
64 parentheses, like in |
|
65 |
|
66 FT_ERROR(( "your %s is not %s\n", "foo", "bar" )); |
|
67 |
|
68 |
|
69 2. FT_ASSERT( condition ) |
|
70 |
|
71 This macro is used to check strong assertions at runtime. If its |
|
72 condition isn't TRUE, the program will abort with a panic message. |
|
73 Its code is compiled when either FT_DEBUG_LEVEL_ERROR or |
|
74 FT_DEBUG_LEVEL_TRACE are defined. You don't need double parentheses |
|
75 here. For example |
|
76 |
|
77 FT_ASSERT( ptr != NULL ); |
|
78 |
|
79 |
|
80 3. FT_TRACE( level, (message...) ) |
|
81 |
|
82 The FT_TRACE macro is used to send general-purpose debugging |
|
83 messages during program execution. This macro uses an *implicit* |
|
84 macro named FT_COMPONENT used to name the current FreeType component |
|
85 being run. |
|
86 |
|
87 The developer should always define FT_COMPONENT as appropriate, for |
|
88 example as in |
|
89 |
|
90 #undef FT_COMPONENT |
|
91 #define FT_COMPONENT trace_io |
|
92 |
|
93 The value of the FT_COMPONENT macro is an enumeration named |
|
94 trace_XXXX where XXXX is one of the component names defined in the |
|
95 internal file `freetype/internal/fttrace.h'. If you modify FreeType |
|
96 source and insert new trace_XXXX macro, you must register it in |
|
97 fttrace.h. If you insert or remove many trace macros, you can check |
|
98 the undefined or the unused trace macro by src/tools/chktrcmp.py. |
|
99 |
|
100 Each such component is assigned a `debug level', ranging from 0 |
|
101 to 7, through the use of the FT2_DEBUG environment variable |
|
102 (described below) when a program linked with FreeType starts. |
|
103 |
|
104 When FT_TRACE is called, its level is compared to the one of the |
|
105 corresponding component. Messages with trace levels *higher* than |
|
106 the corresponding component level are filtered and never printed. |
|
107 |
|
108 This means that trace messages with level 0 are always printed, |
|
109 those with level 2 are only printed when the component level is *at |
|
110 least* 2. |
|
111 |
|
112 The second parameter to FT_TRACE must contain parentheses and |
|
113 correspond to a printf-like call, as in |
|
114 |
|
115 FT_TRACE( 2, ( "your %s is not %s\n", "foo", "bar" ) ) |
|
116 |
|
117 The shortcut macros FT_TRACE0, FT_TRACE1, FT_TRACE2, ..., FT_TRACE7 |
|
118 can be used with constant level indices, and are much cleaner to |
|
119 use, as in |
|
120 |
|
121 FT_TRACE2(( "your %s is not %s\n", "foo", "bar" )); |
|
122 |
|
123 |
|
124 III. Environment variables |
|
125 -------------------------- |
|
126 |
|
127 The following environment variables control debugging output and |
|
128 behaviour of FreeType at runtime. |
|
129 |
|
130 |
|
131 FT2_DEBUG |
|
132 |
|
133 This variable is only used when FreeType is built with |
|
134 FT_DEBUG_LEVEL_TRACE defined. It contains a list of component level |
|
135 definitions, following this format: |
|
136 |
|
137 component1:level1 component2:level2 component3:level3 ... |
|
138 |
|
139 where `componentX' is the name of a tracing component, as defined in |
|
140 `fttrace.h', but without the `trace_' prefix. `levelX' is the |
|
141 corresponding level to use at runtime. |
|
142 |
|
143 `any' is a special component name that will be interpreted as |
|
144 `any/all components'. For example, the following definitions |
|
145 |
|
146 set FT2_DEBUG=any:2 memory:5 io:4 (on Windows) |
|
147 export FT2_DEBUG="any:2 memory:5 io:4" (on Linux with bash) |
|
148 |
|
149 both stipulate that all components should have level 2, except for |
|
150 the memory and io components which will be set to trace levels 5 and |
|
151 4, respectively. |
|
152 |
|
153 |
|
154 FT2_DEBUG_MEMORY |
|
155 |
|
156 This environment variable, when defined, tells FreeType to use a |
|
157 debugging memory manager that will track leaking memory blocks as |
|
158 well as other common errors like double frees. It is also capable |
|
159 of reporting _where_ the leaking blocks were allocated, which |
|
160 considerably saves time when debugging new additions to the library. |
|
161 |
|
162 This code is only compiled when FreeType is built with the |
|
163 FT_DEBUG_MEMORY macro #defined in `ftoption.h' though, it will be |
|
164 ignored in other builds. |
|
165 |
|
166 |
|
167 FT2_ALLOC_TOTAL_MAX |
|
168 |
|
169 This variable is ignored if FT2_DEBUG_MEMORY is not defined. It |
|
170 allows you to specify a maximum heap size for all memory allocations |
|
171 performed by FreeType. This is very useful to test the robustness |
|
172 of the font engine and programs that use it in tight memory |
|
173 conditions. |
|
174 |
|
175 If it is undefined, or if its value is not strictly positive, then |
|
176 no allocation bounds are checked at runtime. |
|
177 |
|
178 |
|
179 FT2_ALLOC_COUNT_MAX |
|
180 |
|
181 This variable is ignored if FT2_DEBUG_MEMORY is not defined. It |
|
182 allows you to specify a maximum number of memory allocations |
|
183 performed by FreeType before returning the error |
|
184 FT_Err_Out_Of_Memory. This is useful for debugging and testing the |
|
185 engine's robustness. |
|
186 |
|
187 If it is undefined, or if its value is not strictly positive, then |
|
188 no allocation bounds are checked at runtime. |
|
189 |
|
190 ------------------------------------------------------------------------ |
|
191 |
|
192 Copyright 2002, 2003, 2004, 2005, 2009 by |
|
193 David Turner, Robert Wilhelm, and Werner Lemberg. |
|
194 |
|
195 This file is part of the FreeType project, and may only be used, |
|
196 modified, and distributed under the terms of the FreeType project |
|
197 license, LICENSE.TXT. By continuing to use, modify, or distribute this |
|
198 file you indicate that you have read the license and understand and |
|
199 accept it fully. |
|
200 |
|
201 |
|
202 --- end of DEBUG --- |
|