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| <title>Debugging with GDB: Breakpoint-related Warnings</title> |
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| <a name="Breakpoint_002drelated-Warnings"></a> |
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| 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> [<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> |
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| <a name="g_t_0060_0060Breakpoint-address-adjusted_002e_002e_002e_0027_0027"></a> |
| <h4 class="subsection">5.1.12 “Breakpoint address adjusted...”</h4> |
| <a name="index-breakpoint-address-adjusted"></a> |
| |
| <p>Some processor architectures place constraints on the addresses at |
| which breakpoints may be placed. For architectures thus constrained, |
| <small>GDB</small> will attempt to adjust the breakpoint’s address to comply |
| with the constraints dictated by the architecture. |
| </p> |
| <p>One example of such an architecture is the Fujitsu FR-V. The FR-V is |
| a VLIW architecture in which a number of RISC-like instructions may be |
| bundled together for parallel execution. The FR-V architecture |
| constrains the location of a breakpoint instruction within such a |
| bundle to the instruction with the lowest address. <small>GDB</small> |
| honors this constraint by adjusting a breakpoint’s address to the |
| first in the bundle. |
| </p> |
| <p>It is not uncommon for optimized code to have bundles which contain |
| instructions from different source statements, thus it may happen that |
| a breakpoint’s address will be adjusted from one source statement to |
| another. Since this adjustment may significantly alter <small>GDB</small>’s |
| breakpoint related behavior from what the user expects, a warning is |
| printed when the breakpoint is first set and also when the breakpoint |
| is hit. |
| </p> |
| <p>A warning like the one below is printed when setting a breakpoint |
| that’s been subject to address adjustment: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">warning: Breakpoint address adjusted from 0x00010414 to 0x00010410. |
| </pre></div> |
| |
| <p>Such warnings are printed both for user settable and <small>GDB</small>’s |
| internal breakpoints. If you see one of these warnings, you should |
| verify that a breakpoint set at the adjusted address will have the |
| desired affect. If not, the breakpoint in question may be removed and |
| other breakpoints may be set which will have the desired behavior. |
| E.g., it may be sufficient to place the breakpoint at a later |
| instruction. A conditional breakpoint may also be useful in some |
| cases to prevent the breakpoint from triggering too often. |
| </p> |
| <p><small>GDB</small> will also issue a warning when stopping at one of these |
| adjusted breakpoints: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">warning: Breakpoint 1 address previously adjusted from 0x00010414 |
| to 0x00010410. |
| </pre></div> |
| |
| <p>When this warning is encountered, it may be too late to take remedial |
| action except in cases where the breakpoint is hit earlier or more |
| frequently than expected. |
| </p> |
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| 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> [<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> |
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