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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

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  18. <title>Breakpoint-related Warnings (Debugging with GDB)</title>

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  27. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  28. <link href="Breakpoints.html#Breakpoints" rel="up" title="Breakpoints">

  29. <link href="Continuing-and-Stepping.html#Continuing-and-Stepping" rel="next" title="Continuing and Stepping">

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  63. <a name="Breakpoint_002drelated-Warnings"></a>

  64. <div class="header">

  65. <p>

  66. Previous: <a href="Error-in-Breakpoints.html#Error-in-Breakpoints" accesskey="p" rel="prev">Error in Breakpoints</a>, Up: <a href="Breakpoints.html#Breakpoints" accesskey="u" rel="up">Breakpoints</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>

  67. </div>

  68. <hr>

  69. <a name="g_t_0060_0060Breakpoint-address-adjusted_002e_002e_002e_0027_0027"></a>

  70. <h4 class="subsection">5.1.12 &ldquo;Breakpoint address adjusted...&rdquo;</h4>

  71. <a name="index-breakpoint-address-adjusted"></a>

  72. 

  73. <p>Some processor architectures place constraints on the addresses at

  74. which breakpoints may be placed.  For architectures thus constrained,

  75. <small>GDB</small> will attempt to adjust the breakpoint&rsquo;s address to comply

  76. with the constraints dictated by the architecture.

  77. </p>

  78. <p>One example of such an architecture is the Fujitsu FR-V.  The FR-V is

  79. a VLIW architecture in which a number of RISC-like instructions may be

  80. bundled together for parallel execution.  The FR-V architecture

  81. constrains the location of a breakpoint instruction within such a

  82. bundle to the instruction with the lowest address.  <small>GDB</small>

  83. honors this constraint by adjusting a breakpoint&rsquo;s address to the

  84. first in the bundle.

  85. </p>

  86. <p>It is not uncommon for optimized code to have bundles which contain

  87. instructions from different source statements, thus it may happen that

  88. a breakpoint&rsquo;s address will be adjusted from one source statement to

  89. another.  Since this adjustment may significantly alter <small>GDB</small>&rsquo;s

  90. breakpoint related behavior from what the user expects, a warning is

  91. printed when the breakpoint is first set and also when the breakpoint

  92. is hit.

  93. </p>

  94. <p>A warning like the one below is printed when setting a breakpoint

  95. that&rsquo;s been subject to address adjustment:

  96. </p>

  97. <div class="smallexample">

  98. <pre class="smallexample">warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.

  99. </pre></div>

  100. 

  101. <p>Such warnings are printed both for user settable and <small>GDB</small>&rsquo;s

  102. internal breakpoints.  If you see one of these warnings, you should

  103. verify that a breakpoint set at the adjusted address will have the

  104. desired affect.  If not, the breakpoint in question may be removed and

  105. other breakpoints may be set which will have the desired behavior.

  106. E.g., it may be sufficient to place the breakpoint at a later

  107. instruction.  A conditional breakpoint may also be useful in some

  108. cases to prevent the breakpoint from triggering too often.

  109. </p>

  110. <p><small>GDB</small> will also issue a warning when stopping at one of these

  111. adjusted breakpoints:

  112. </p>

  113. <div class="smallexample">

  114. <pre class="smallexample">warning: Breakpoint 1 address previously adjusted from 0x00010414

  115. to 0x00010410.

  116. </pre></div>

  117. 

  118. <p>When this warning is encountered, it may be too late to take remedial

  119. action except in cases where the breakpoint is hit earlier or more

  120. frequently than expected.

  121. </p>

  122. <hr>

  123. <div class="header">

  124. <p>

  125. Previous: <a href="Error-in-Breakpoints.html#Error-in-Breakpoints" accesskey="p" rel="prev">Error in Breakpoints</a>, Up: <a href="Breakpoints.html#Breakpoints" accesskey="u" rel="up">Breakpoints</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>

  126. </div>

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