Turn warnings and hints on or off: what changed

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Title: Turn warnings and hints on or off

New		Line
1	+	There are several ways to control the behavior of warnings in both the Lazarus IDE and in the source code itself. Some warnings and hints are not very useful in a particular case so you want to hide them from view. On the other hand, if you would hide warnings or hints globally, you may want to turn a particular warning or hint explicitly on for a particular piece of your code.
2	+
3	+	``` pascal
4	+	procedure TForm.Button1Click(sender:Tobject);
5	+	begin
6	+	// Do something that does not use sender
7	+	Form1.Button1.Caption := 'Test';
8	+	end;
9	+	```
10	+
11	+	This will generate a hint that parameter sender is not used. Doh. I can see that! Problem is that this hint turns up all over the place and I know what it means. How do I hide them?
12	+
13	+	# Lazarus IDE options
14	+
15	+	The Lazarus IDE can control hints and warnings in two ways:
16	+
17	+	- Globally through the Project Options menu
18	+	- Using an IDE macro
19	+
20	+	## Global IDE option
21	+
22	+	Go to the Project Options-\>Compiler Options-\>Messages and uncheck 'Hint:Paramater "\$1" not used'.
23	+
24	+	This will turn of this particular hint for your whole project.\
25	+	If you would like to turn off this hint for all your projects, you can check the left bottom checkbox 'Set compiler options as default'.
26	+
27	+	![](/wiki-images/e/e3/Lazarusglobal.png)
28	+
29	+	## Local IDE option
30	+
31	+	In the Lazarus IDE you can make use of the {%H-} IDE macro to turn hints off for a particular parameter.\
32	+	Of course {%H+} will turn hints on.
33	+
34	+	``` pascal
35	+	procedure FormMouseDown(Sender: TObject; {%H-}Button: TMouseButton;
36	+	{%H-}Shift: TShiftState; {%H-}X, {%H-}Y: Integer);
37	+	```
38	+
39	+	Note that this turns off ALL hints for that parameter, not just the 'is not used' hint, so be careful.
40	+
41	+	# Source code and compiler options
42	+
43	+	The options as described above will only work within the Lazarus IDE.
44	+
45	+	It won't work in any other IDE, not even de FPC textmode IDE. The compiler output will still emit warnings and hints.
46	+
47	+	Luckily there are several other options to control hints and warnings in the source code itself.
48	+
49	+	## Control all warnings per unit:
50	+
51	+	Add
52	+
53	+	``` pascal
54	+	{$warnings off}
55	+	```
56	+
57	+	or resp.
58	+
59	+	``` pascal
60	+	{$warnings on}
61	+	```
62	+
63	+	just after the unit name.
64	+
65	+	## Control all hints per unit:
66	+
67	+	Add
68	+
69	+	``` pascal
70	+	{$hints off}
71	+	```
72	+
73	+	or resp.
74	+
75	+	``` pascal
76	+	{$hints on}
77	+	```
78	+
79	+	just after the unit name.
80	+
81	+	## Control specific warnings:
82	+
83	+	Add
84	+
85	+	``` pascal
86	+	{$warn <number> off}
87	+	```
88	+
89	+	just after the unit name. See the example below. You can also use this construct if you want all warnings off but some specific warning(s) on:
90	+
91	+	``` pascal
92	+	{$warnings off}{$warn <number> on}
93	+	```
94	+
95	+	## Control Specific Warnings or hints per piece of code:
96	+
97	+	You can control this very finely grained by using {\$push} and {\$pop} around a block of code. This does not have to be a method body as long it is a block, e.g. begin/end,repeat/until,/while do, try/finally etc.
98	+
99	+	``` pascal
100	+	procedure withunusedparameter(const testme:integer);
101	+	{$push}{$warn 5024 off}
102	+	begin
103	+	//
104	+	end;
105	+	{$pop}
106	+	begin
107	+	withunusedparameter(100);
108	+	end.
109	+	```
110	+
111	+	# Obtaining the warnings and hints numbers to suppress
112	+
113	+	You can obtain the needed numbers by compiling your code once with line info on and with -vwhilq
114	+
115	+	This will show both the numbers and the messages and the line numbers where they are found.
116	+
117	+	The other way to obtain hint, notice or warning number is to search inside FP repository for source of your current FPC version.
118	+
119	+	All of the messages with its own description is stored in \<FPC source dir\>/msg/error\<language\>.msg
120	+
121	+	This file is also have header, which provides explanation how error/notice/hint/warning constants are constructed.
122	+
123	+	For the English language it's contains following:
124	+
125	+	``` pascal
126	+	# CodePage 20127
127	+
128	+	#
129	+	# The constants are build in the following order:
130	+	# <part>_<type>_<txtidentifier>
131	+	#
132	+	# <part> is the part of the compiler the message is used
133	+	# asmr_ assembler parsing
134	+	# asmw_ assembler writing/binary writers
135	+	# unit_ unit handling
136	+	# option_ command line parameter parsing
137	+	# scan_ scanner
138	+	# parser_ parser
139	+	# type_ type checking
140	+	# general_ general info
141	+	# exec_ calls to assembler, external linker, binder
142	+	# link_ internal linker
143	+	# package_ package handling
144	+	#
145	+	# <type> the type of the message it should normally used for
146	+	# f_ fatal error
147	+	# e_ error
148	+	# w_ warning
149	+	# n_ note
150	+	# h_ hint
151	+	# i_ info
152	+	# l_ add linenumber
153	+	# u_ used
154	+	# t_ tried
155	+	# c_ conditional
156	+	# d_ debug message
157	+	# x_ executable informations
158	+	# o_ normal (e.g., "press enter to continue")
159	+	#
160	+	# <type> can contain a minus sign at the beginning to mark that
161	+	# the message is off by default. Look at type_w_explicit_string_cast
162	+	# for example.
163	+	```
164	+
165	+	So, to find your warning/notice/etc, you just need to search the message body. For the example, it can be \<unit "Pas2Js.pas" not used in main.pas\>, to find this warning, you need to replace all of the local data in message body with \$\< data number \>,
166	+
167	+	`for this situation it will be: <Unit "$1" not used in $2>;`
168	+
169	+	After that, you can find the required message just by finding its body in errors\<language\>.msg file, you will find the following:
170	+
171	+	``` pascal
172	+	sym_n_unit_not_used=05023_H_Unit "$1" not used in $2
173	+	% The unit referenced in the \var{uses} clause is not used.
174	+	```
175	+
176	+	So, the actual notice number is 05023.
177	+
178	+	Based on that number you can decide to suppress the warning or hint globally, per unit or per routine, depending on what you need.
179	+
180	+	For example, if you want to suppress unused parameters you can subsequently compile with -vm5024.
181	+
182	+	With the -vm compiler option you can use multiple warning and hint numbers separated by a comma. Or you can write:
183	+
184	+	``` pascal
185	+	{$warn 5024 off}
186	+	```
187	+
188	+	This needs to be done for each number separately.
189	+
190	+	See also:
191	+
192	+	---
193	+	From the Free Pascal wiki, page "Turn warnings and hints on or off", as it stood on 2020-03-02 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).

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