gdb: Breakpoint-related Warnings
5.1.12 "Breakpoint address adjusted..."
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Some processor architectures place constraints on the addresses at which
breakpoints may be placed. For architectures thus constrained, GDB will
attempt to adjust the breakpoint's address to comply with the
constraints dictated by the architecture.
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. GDB honors this constraint
by adjusting a breakpoint's address to the first in the bundle.
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 GDB'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.
A warning like the one below is printed when setting a breakpoint
that's been subject to address adjustment:
warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
Such warnings are printed both for user settable and GDB'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.
GDB will also issue a warning when stopping at one of these adjusted
breakpoints:
warning: Breakpoint 1 address previously adjusted from 0x00010414
to 0x00010410.
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.
Info Catalog
gdb: Error in Breakpoints
gdb: Breakpoints