1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 6. Coding Suggestions</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt02.html" title="Part II. Samba Basics"><link rel="prev" href="internals.html" title="Chapter 5. Samba Internals"><link rel="next" href="contributing.html" title="Chapter 7. Contributing code"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 6. Coding Suggestions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="internals.html">Prev</a> </td><th width="60%" align="center">Part II. Samba Basics</th><td width="20%" align="right"> <a accesskey="n" href="contributing.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="CodingSuggestions"></a>Chapter 6. Coding Suggestions</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Steve</span> <span class="surname">French</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Simo</span> <span class="surname">Sorce</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Andrew</span> <span class="surname">Bartlett</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Tim</span> <span class="surname">Potter</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Martin</span> <span class="surname">Pool</span></h3></div></div></div></div><p>
2 So you want to add code to Samba ...
4 One of the daunting tasks facing a programmer attempting to write code for
5 Samba is understanding the various coding conventions used by those most
6 active in the project. These conventions were mostly unwritten and helped
7 improve either the portability, stability or consistency of the code. This
8 document will attempt to document a few of the more important coding
9 practices used at this time on the Samba project. The coding practices are
10 expected to change slightly over time, and even to grow as more is learned
11 about obscure portability considerations. Two existing documents
12 <code class="filename">samba/source/internals.doc</code> and
13 <code class="filename">samba/source/architecture.doc</code> provide
14 additional information.
16 The loosely related question of coding style is very personal and this
17 document does not attempt to address that subject, except to say that I
18 have observed that eight character tabs seem to be preferred in Samba
19 source. If you are interested in the topic of coding style, two oft-quoted
22 <a href="http://lxr.linux.no/source/Documentation/CodingStyle" target="_top">http://lxr.linux.no/source/Documentation/CodingStyle</a>
24 <a href="http://www.fsf.org/prep/standards_toc.html" target="_top">http://www.fsf.org/prep/standards_toc.html</a>
26 But note that coding style in Samba varies due to the many different
27 programmers who have contributed.
29 Following are some considerations you should use when adding new code to
30 Samba. First and foremost remember that:
32 Portability is a primary consideration in adding function, as is network
33 compatability with de facto, existing, real world CIFS/SMB implementations.
34 There are lots of platforms that Samba builds on so use caution when adding
35 a call to a library function that is not invoked in existing Samba code.
36 Also note that there are many quite different SMB/CIFS clients that Samba
37 tries to support, not all of which follow the SNIA CIFS Technical Reference
38 (or the earlier Microsoft reference documents or the X/Open book on the SMB
41 Here are some other suggestions:
42 </p><div class="orderedlist"><ol type="1"><li><p>
43 use d_printf instead of printf for display text
44 reason: enable auto-substitution of translated language text
46 use SAFE_FREE instead of free
47 reason: reduce traps due to null pointers
49 don't use bzero use memset, or ZERO_STRUCT and ZERO_STRUCTP macros
52 don't use strcpy and strlen (use safe_* equivalents)
53 reason: to avoid traps due to buffer overruns
55 don't use getopt_long, use popt functions instead
58 explicitly add const qualifiers on parm passing in functions where parm
59 is input only (somewhat controversial but const can be #defined away)
61 when passing a va_list as an arg, or assigning one to another
62 please use the VA_COPY() macro
63 reason: on some platforms, va_list is a struct that must be
64 initialized in each function...can SEGV if you don't.
66 discourage use of threads
67 reason: portability (also see architecture.doc)
69 don't explicitly include new header files in C files - new h files
70 should be included by adding them once to includes.h
73 don't explicitly extern functions (they are autogenerated by
74 "make proto" into proto.h)
77 use endian safe macros when unpacking SMBs (see byteorder.h and
79 reason: not everyone uses Intel
81 Note Unicode implications of charset handling (see internals.doc). See
82 pull_* and push_* and convert_string functions.
83 reason: Internationalization
85 Don't assume English only
88 Try to avoid using in/out parameters (functions that return data which
89 overwrites input parameters)
90 reason: Can cause stability problems
92 Ensure copyright notices are correct, don't append Tridge's name to code
93 that he didn't write. If you did not write the code, make sure that it
94 can coexist with the rest of the Samba GPLed code.
96 Consider usage of DATA_BLOBs for length specified byte-data.
99 Take advantage of tdbs for database like function
102 Don't access the SAM_ACCOUNT structure directly, they should be accessed
103 via pdb_get...() and pdb_set...() functions.
104 reason: stability, consistency
106 Don't check a password directly against the passdb, always use the
107 check_password() interface.
108 reason: long term pluggability
110 Try to use asprintf rather than pstrings and fstrings where possible
112 Use normal C comments / * instead of C++ comments // like
113 this. Although the C++ comment format is part of the C99
114 standard, some older vendor C compilers do not accept it.
116 Try to write documentation for API functions and structures
117 explaining the point of the code, the way it should be used, and
118 any special conditions or results. Mark these with a double-star
119 comment start / ** so that they can be picked up by Doxygen, as in
122 Keep the scope narrow. This means making functions/variables
123 static whenever possible. We don't want our namespace
124 polluted. Each module should have a minimal number of externally
125 visible functions or variables.
127 Use function pointers to keep knowledge about particular pieces of
128 code isolated in one place. We don't want a particular piece of
129 functionality to be spread out across lots of places - that makes
130 for fragile, hand to maintain code. Instead, design an interface
131 and use tables containing function pointers to implement specific
132 functionality. This is particularly important for command
135 Think carefully about what it will be like for someone else to add
136 to and maintain your code. If it would be hard for someone else to
137 maintain then do it another way.
138 </p></li></ol></div><p>
139 The suggestions above are simply that, suggestions, but the information may
140 help in reducing the routine rework done on new code. The preceeding list
141 is expected to change routinely as new support routines and macros are
143 </p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="internals.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="contributing.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 5. Samba Internals </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 7. Contributing code</td></tr></table></div></body></html>
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