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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). |
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37 ** |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \example xmlpatterns/xquery/globalVariables |
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44 \title C++ Source Code Analyzer Example |
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45 |
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46 This example uses XQuery and the \c xmlpatterns command line utility to |
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47 query C++ source code. |
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48 |
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49 \tableofcontents |
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50 |
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51 \section1 Introduction |
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52 |
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53 Suppose we want to analyze C++ source code to find coding standard |
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54 violations and instances of bad or inefficient patterns. We can do |
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55 it using the common searching and pattern matching utilities to |
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56 process the C++ files (e.g., \c{grep}, \c{sed}, and \c{awk}). Now |
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57 we can also use XQuery with the QtXmlPatterns module. |
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58 |
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59 An extension to the \c{g++} open source C++ compiler |
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60 (\l{http://public.kitware.com/GCC_XML/HTML/Index.html} {GCC-XML}) |
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61 generates an XML description of C++ source code declarations. This |
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62 XML description can then be processed by QtXmlPatterns using |
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63 XQueries to navigate the XML description of the C++ source and |
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64 produce a report. Consider the problem of finding mutable global |
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65 variables: |
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66 |
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67 \section2 Reporting Uses of Mutable Global Variables |
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68 |
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69 Suppose we want to introduce threading to a C++ application that |
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70 was originally written without threading. In a threaded program, |
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71 mutable global variables can cause bugs, because one thread might |
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72 change a global variable that other threads are reading, or two |
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73 threads might try to set the same global variable. So when |
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74 converting our program to use threading, one of the things we must |
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75 do is protect the global variables to prevent the bugs described |
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76 above. How can we use XQuery and |
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77 \l{http://public.kitware.com/GCC_XML/HTML/Index.html} {GCC-XML} to |
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78 find the variables that need protecting? |
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79 |
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80 \section3 A C++ application |
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81 |
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82 Consider the declarations in this hypothetical C++ application: |
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83 |
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84 \snippet examples/xmlpatterns/xquery/globalVariables/globals.cpp 0 |
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85 |
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86 \section3 The XML description of the C++ application |
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87 |
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88 Submitting this C++ source to |
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89 \l{http://public.kitware.com/GCC_XML/HTML/Index.html} {GCC-XML} |
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90 produces this XML description: |
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91 |
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92 \quotefromfile examples/xmlpatterns/xquery/globalVariables/globals.gccxml |
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93 \printuntil |
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94 |
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95 \section3 The XQuery for finding global variables |
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96 |
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97 We need an XQuery to find the global variables in the XML |
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98 description. Here is our XQuery source. We walk through it in |
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99 \l{XQuery Code Walk-Through}. |
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100 |
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101 \quotefromfile examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq |
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102 \printuntil |
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103 |
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104 \section3 Running the XQuery |
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105 |
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106 To run the XQuery using the \c xmlpatterns command line utility, |
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107 enter the following command: |
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108 |
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109 \code |
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110 xmlpatterns reportGlobals.xq -param fileToOpen=globals.gccxml -output globals.html |
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111 \endcode |
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112 |
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113 \section3 The XQuery output |
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114 |
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115 The \c xmlpatterns command loads and parses \c globals.gccxml, |
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116 runs the XQuery \c reportGlobals.xq, and generates this report: |
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117 |
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118 \raw HTML |
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119 <html xmlns="http://www.w3.org/1999/xhtml/" xml:lang="en" lang="en"> |
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120 <head> |
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121 <title>Global variables report for globals.gccxml</title> |
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122 </head> |
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123 <style type="text/css"> |
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124 .details |
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125 { |
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126 text-align: left; |
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127 font-size: 80%; |
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128 color: blue |
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129 } |
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130 .variableName |
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131 { |
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132 font-family: courier; |
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133 color: blue |
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134 } |
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135 </style> |
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136 <body> |
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137 <p class="details">Start report: 2008-12-16T13:43:49.65Z</p> |
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138 <p>Global variables with complex types:</p> |
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139 <ol> |
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140 <li> |
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141 <span class="variableName">mutableComplex1</span> in globals.cpp at line 14</li> |
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142 <li> |
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143 <span class="variableName">mutableComplex2</span> in globals.cpp at line 15</li> |
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144 <li> |
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145 <span class="variableName">constComplex1</span> in globals.cpp at line 16</li> |
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146 <li> |
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147 <span class="variableName">constComplex2</span> in globals.cpp at line 17</li> |
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148 </ol> |
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149 <p>Mutable global variables with primitives types:</p> |
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150 <ol> |
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151 <li> |
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152 <span class="variableName">mutablePrimitive1</span> in globals.cpp at line 1</li> |
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153 <li> |
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154 <span class="variableName">mutablePrimitive2</span> in globals.cpp at line 2</li> |
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155 </ol> |
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156 <p class="details">End report: 2008-12-16T13:43:49.65Z</p> |
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157 </body> |
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158 </html> |
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159 \endraw |
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160 |
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161 \section1 XQuery Code Walk-Through |
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162 |
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163 The XQuery source is in |
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164 \c{examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq} |
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165 It begins with two variable declarations that begin the XQuery: |
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166 |
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167 \quotefromfile examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq |
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168 \skipto declare variable |
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169 \printto (: |
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170 |
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171 The first variable, \c{$fileToOpen}, appears in the \c xmlpatterns |
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172 command shown earlier, as \c{-param fileToOpen=globals.gccxml}. |
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173 This binds the variable name to the file name. This variable is |
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174 then used in the declaration of the second variable, \c{$inDoc}, |
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175 as the parameter to the |
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176 \l{http://www.w3.org/TR/xpath-functions/#func-doc} {doc()} |
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177 function. The \c{doc()} function returns the document node of |
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178 \c{globals.gccxml}, which is assigned to \c{$inDoc} to be used |
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179 later in the XQuery as the root node of our searches for global |
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180 variables. |
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181 |
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182 Next skip to the end of the XQuery, where the \c{<html>} element |
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183 is constructed. The \c{<html>} will contain a \c{<head>} element |
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184 to specify a heading for the html page, followed by some style |
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185 instructions for displaying the text, and then the \c{<body>} |
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186 element. |
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187 |
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188 \quotefromfile examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq |
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189 \skipto <html xmlns |
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190 \printuntil |
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191 |
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192 The \c{<body>} element contains a call to the \c{local:report()} |
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193 function, which is where the query does the "heavy lifting." Note |
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194 the two \c{return} clauses separated by the \e {comma operator} |
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195 about halfway down: |
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196 |
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197 \quotefromfile examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq |
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198 \skipto declare function local:report() |
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199 \printuntil }; |
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200 |
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201 The \c{return} clauses are like two separate queries. The comma |
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202 operator separating them means that both \c{return} clauses are |
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203 executed and both return their results, or, rather, both output |
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204 their results. The first \c{return} clause searches for global |
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205 variables with complex types, and the second searches for mutable |
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206 global variables with primitive types. |
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207 |
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208 Here is the html generated for the \c{<body>} element. Compare |
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209 it with the XQuery code above: |
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210 |
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211 \quotefromfile examples/xmlpatterns/xquery/globalVariables/globals.html |
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212 \skipto <body> |
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213 \printuntil </body> |
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214 |
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215 The XQuery declares three more local functions that are called in |
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216 turn by the \c{local:report()} function. \c{isComplexType()} |
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217 returns true if the variable has a complex type. The variable can |
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218 be mutable or const. |
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219 |
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220 \quotefromfile examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq |
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221 \skipto declare function local:isComplexType |
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222 \printuntil }; |
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223 |
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224 \c{isPrimitive()} returns true if the variable has a primitive |
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225 type. The variable must be mutable. |
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226 |
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227 \quotefromfile examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq |
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228 \skipto declare function local:isPrimitive |
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229 \printuntil }; |
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230 |
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231 \c{location()} returns a text constructed from the variable's file |
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232 and line number attributes. |
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233 |
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234 \quotefromfile examples/xmlpatterns/xquery/globalVariables/reportGlobals.xq |
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235 \skipto declare function local:location |
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236 \printuntil }; |
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237 |
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238 */ |