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tracing: dedup TRACE macros & rename to TRACEPOINT

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This deduplicates the TRACEx macros by using systemtaps STAP_PROBEV[0]
variadic macro instead of the DTrace compability DTRACE_PROBE[1] macros.
Bitcoin Core never had DTrace tracepoints, so we don't need to use the
drop-in replacement for it. As noted in pr25541[2], these macros aren't
compatibile with DTrace on macOS anyway.

This also renames the TRACEx macro to TRACEPOINT to clarify what the
macro does: inserting a tracepoint vs tracing (logging) something.

[0]: https://sourceware.org/git/?p=systemtap.git;a=blob;f=includes/sys/sdt.h;h=24d5e01c37805e55c36f7202e5d4e821b85167a1;hb=ecab2afea46099b4e7dfd551462689224afdbe3a#l407
[1]: https://sourceware.org/git/?p=systemtap.git;a=blob;f=includes/sys/sdt.h;h=24d5e01c37805e55c36f7202e5d4e821b85167a1;hb=ecab2afea46099b4e7dfd551462689224afdbe3a#l490
[2]: https://github.com/bitcoin/bitcoin/pull/25541/files#diff-553886c5f808e01e3452c7b21e879cc355da388ef7680bf310f6acb926d43266R30-R31

Co-authored-by: Martin Leitner-Ankerl <martin.ankerl@gmail.com>
This commit is contained in:
0xb10c
2023-11-23 11:06:17 +01:00
parent 1c7ca6e64d
commit d524c1ec06
11 changed files with 62 additions and 70 deletions
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36
doc/tracing.md
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@@ -265,35 +265,19 @@ Arguments passed:
## Adding tracepoints to Bitcoin Core
To add a new tracepoint, `#include <util/trace.h>` in the compilation unit where
the tracepoint is inserted. Use one of the `TRACEx` macros listed below
depending on the number of arguments passed to the tracepoint. Up to 12
arguments can be provided. The `context` and `event` specify the names by which
the tracepoint is referred to. Please use `snake_case` and try to make sure that
the tracepoint names make sense even without detailed knowledge of the
implementation details. Do not forget to update the tracepoint list in this
Use the `TRACEPOINT` macro to add a new tracepoint. If not yet included, include
`util/trace.h` (defines the tracepoint macros) with `#include <util/trace.h>`.
Each tracepoint needs a `context` and an `event`. Please use `snake_case` and
try to make sure that the tracepoint names make sense even without detailed
knowledge of the implementation details. You can pass zero to twelve arguments
to the tracepoint. Do not forget to update the tracepoint list in this
document.
```c
#define TRACE(context, event)
#define TRACE1(context, event, a)
#define TRACE2(context, event, a, b)
#define TRACE3(context, event, a, b, c)
#define TRACE4(context, event, a, b, c, d)
#define TRACE5(context, event, a, b, c, d, e)
#define TRACE6(context, event, a, b, c, d, e, f)
#define TRACE7(context, event, a, b, c, d, e, f, g)
#define TRACE8(context, event, a, b, c, d, e, f, g, h)
#define TRACE9(context, event, a, b, c, d, e, f, g, h, i)
#define TRACE10(context, event, a, b, c, d, e, f, g, h, i, j)
#define TRACE11(context, event, a, b, c, d, e, f, g, h, i, j, k)
#define TRACE12(context, event, a, b, c, d, e, f, g, h, i, j, k, l)
```
For example:
For example, a tracepoint in the `net` context for the event `inbound_message`
and six arguments:
```C++
TRACE6(net, inbound_message,
TRACEPOINT(net, inbound_message,
pnode->GetId(),
pnode->m_addr_name.c_str(),
pnode->ConnectionTypeAsString().c_str(),
@@ -347,7 +331,7 @@ first six argument fields. Binary data can be placed in later arguments. The BCC
supports reading from all 12 arguments.
#### Strings as C-style String
Generally, strings should be passed into the `TRACEx` macros as pointers to
Generally, strings should be passed into the `TRACEPOINT` macros as pointers to
C-style strings (a null-terminated sequence of characters). For C++
`std::strings`, [`c_str()`] can be used. It's recommended to document the
maximum expected string size if known.