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Follow-up to P2546, "Debugging Support" #7642

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Merged
merged 7 commits into from
Mar 15, 2025
Merged

Follow-up to P2546, "Debugging Support" #7642

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6e3a4b5
Re-word `breakpoint` to fix untrue statement-of-fact
Feb 13, 2025
fe98e6e
Case where resumption does not resume as if the function is invoked
Feb 13, 2025
d817067
breakpoint when no debugger is present
Feb 13, 2025
4d24c66
is_debugger_present: Fix unsupported statement-of-fact
Feb 13, 2025
a5c7585
is_debugger_present: ptrace is not POSIX; LSB uses "tracing process"
Feb 13, 2025
67706d2
is_debugger_present: Clarify intent to avoid false positives
Feb 14, 2025
cb8fc31
Replace newly added "abend"
hubert-reinterpretcast Feb 14, 2025
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24 changes: 14 additions & 10 deletions source/diagnostics.tex
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Expand Up @@ -2447,10 +2447,13 @@
The semantics of this function are \impldef{semantics of \tcode{breakpoint}}.

\begin{note}
When invoked, the execution of the program temporarily halts and execution is
handed to the debugger until such a time as: The program is terminated by the
debugger, or the debugger resumes execution of the program as if the function
was not invoked.
It is intended that, when invoked with a debugger present, the execution of the
program temporarily halts and execution is handed to the debugger until the
program is either terminated by the debugger or the debugger resumes execution
of the program as if the function was not invoked. In particular, there is no
intent for a call to this function to accomodate resumption of the program in a
different manner. If there is no debugger present, execution of the program can
end abnormally.
\end{note}

\end{itemdescr}
Expand Down Expand Up @@ -2491,12 +2494,13 @@
\impldef{default semantics of \tcode{is_debugger_present}}.

\begin{note}
When tracing the execution of a program with a debugger, an implementation
returns \tcode{true}. An implementation performs an immediate query, as needed,
to determine if the program is traced by a debugger. On Windows or equivalent
systems, this can be achieved by calling the \tcode{::IsDebuggerPresent()} Win32
function. On POSIX, this can be achieved by checking for a tracer parent process,
with best effort determination that such a tracer parent process is a debugger.
It is intended that, using an immediate (uncached) query to determine if the
program is being traced by a debugger, an implementation returns \tcode{true}
only when tracing the execution of the program with a debugger. On Windows or
equivalent systems, this can be achieved by calling the
\tcode{::IsDebuggerPresent()} Win32 function. For systems compatible with
ISO/IEC 23360:2021, this can be achieved by checking for a tracing process, with
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This replaces "POSIX" with "Linux Standard Base". Is there a particular reason for that? Does POSIX not cover the needed functionality?

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Although ptrace is present in most UNIX-like systems, it isn't part of POSIX. The LSB is a much narrower scope than POSIX, but it is a standard, unlike families like "BSD" or "SysV". So if we want a standard that includes ptrace, LSB makes sense.

However, the wording never mentions prrace it just talks about "tracing" and "a tracer parent process" which is still meaningful even in e.g. HP-UX which replaced ptrace with ttrace, and in Solaris through ptrace but also via procfs. So maybe it's OK.

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However, the wording never mentions prrace it just talks about "tracing" and "a tracer parent process" which is still meaningful even in e.g. HP-UX which replaced ptrace with ttrace, and in Solaris through ptrace but also via procfs. So maybe it's OK.

Using "POSIX" in conjunction with the handwaving implies that the handwaving is necessarily meaningful for all possible implementations of POSIX. That it is probably meaningful for extant implementations of POSIX does not make me feel any better about using "POSIX" without qualification.

a best-effort determination that such a tracing process is a debugger.
\end{note}

\end{itemdescr}