[#absl-DefaultStackUnwinder]
= xref:absl.adoc[absl]::DefaultStackUnwinder
:relfileprefix: ../
:mrdocs:

Records program counter values of up to `max_depth` frames, skipping the most recent `skip_count` stack frames, and stores their corresponding values in `pcs`. (Note that the frame generated for this call itself is also skipped.) This function acts as a generic stack‐unwinder; prefer usage of the more specific `GetStack{Trace,Frames}{,WithContext}()` functions above.

== Synopsis

Declared in `<absl/debugging/stacktrace.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
extern
int
DefaultStackUnwinder(
    void** pcs,
    int* sizes,
    int max_depth,
    int skip_count,
    void const* uc,
    int* min_dropped_frames);
----

== Description

If you have set your own stack unwinder (with the `SetStackUnwinder()` function above, you can still get the default stack unwinder by calling `DefaultStackUnwinder()`, which will ignore any previously set stack unwinder and use the default one instead.

Because this function is generic, only `pcs` is guaranteed to be non‐null upon return. It is legal for `sizes`, `uc`, and `min_dropped_frames` to all be null when called.

The semantics are the same as the corresponding `GetStack*()` function in the case where `absl::SetStackUnwinder()` was never called. Equivalents are:

null sizes | non‐nullptr sizes |==| null uc | GetStackTrace() | GetStackFrames() | non‐null uc | GetStackTraceWithContext() | GetStackFramesWithContext() | |==|

== Return Value

The number of frames stored in `pcs`.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *pcs*
| Buffer to receive the recorded program counter values.
| *sizes*
| If non‐null, receives the corresponding stack frame sizes.
| *max_depth*
| Maximum number of frames to record.
| *skip_count*
| Number of most recent stack frames to skip.
| *uc*
| Pointer to the signal handler's `ucontext_t` value, or null.
| *min_dropped_frames*
| If non‐null, receives the number of stack frames dropped.
|===


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