98 lines
4.5 KiB
HTML
98 lines
4.5 KiB
HTML
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<title>Breakpoint-related Warnings - Debugging with GDB</title>
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<link rel="up" href="Breakpoints.html#Breakpoints" title="Breakpoints">
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<link rel="prev" href="Error-in-Breakpoints.html#Error-in-Breakpoints" title="Error in Breakpoints">
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<body>
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<div class="node">
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<a name="Breakpoint-related-Warnings"></a>
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<a name="Breakpoint_002drelated-Warnings"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Error-in-Breakpoints.html#Error-in-Breakpoints">Error in Breakpoints</a>,
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Up: <a rel="up" accesskey="u" href="Breakpoints.html#Breakpoints">Breakpoints</a>
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<hr>
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</div>
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<h4 class="subsection">5.1.12 “Breakpoint address adjusted...”</h4>
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<p><a name="index-breakpoint-address-adjusted-348"></a>
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Some processor architectures place constraints on the addresses at
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which breakpoints may be placed. For architectures thus constrained,
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<span class="sc">gdb</span> will attempt to adjust the breakpoint's address to comply
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with the constraints dictated by the architecture.
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<p>One example of such an architecture is the Fujitsu FR-V. The FR-V is
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a VLIW architecture in which a number of RISC-like instructions may be
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bundled together for parallel execution. The FR-V architecture
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constrains the location of a breakpoint instruction within such a
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bundle to the instruction with the lowest address. <span class="sc">gdb</span>
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honors this constraint by adjusting a breakpoint's address to the
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first in the bundle.
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<p>It is not uncommon for optimized code to have bundles which contain
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instructions from different source statements, thus it may happen that
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a breakpoint's address will be adjusted from one source statement to
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another. Since this adjustment may significantly alter <span class="sc">gdb</span>'s
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breakpoint related behavior from what the user expects, a warning is
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printed when the breakpoint is first set and also when the breakpoint
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is hit.
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<p>A warning like the one below is printed when setting a breakpoint
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that's been subject to address adjustment:
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<pre class="smallexample"> warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
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</pre>
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<p>Such warnings are printed both for user settable and <span class="sc">gdb</span>'s
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internal breakpoints. If you see one of these warnings, you should
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verify that a breakpoint set at the adjusted address will have the
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desired affect. If not, the breakpoint in question may be removed and
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other breakpoints may be set which will have the desired behavior.
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E.g., it may be sufficient to place the breakpoint at a later
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instruction. A conditional breakpoint may also be useful in some
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cases to prevent the breakpoint from triggering too often.
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<p><span class="sc">gdb</span> will also issue a warning when stopping at one of these
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adjusted breakpoints:
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<pre class="smallexample"> warning: Breakpoint 1 address previously adjusted from 0x00010414
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to 0x00010410.
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</pre>
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<p>When this warning is encountered, it may be too late to take remedial
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action except in cases where the breakpoint is hit earlier or more
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frequently than expected.
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</body></html>
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