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7c4e78cf63
Enabling "set debug lin-lwp 1" with the MI interpreter doesn't work.
When the sigchld_handler function wants to print a debug output
("sigchld\n"), it uses ui_file_write_async_safe. This ends up in the
default implementation of ui_file::write_async_safe, which aborts GDB.
This patch implements the write_async_safe method for mi_console_file.
The "normal" MI output is line buffered, which means the output
accumulates in m_buffer until a \n is written, at which point it's
flushed in m_raw. The implementation of write_async_safe provided by
this patch bypasses this buffer and writes directly to m_raw. There are
two reasons for this:
(1) Appending to m_buffer (therefore to an std::string) is probably not
async-safe, as it may allocate memory.
(2) We may have a partial output already in m_buffer, so that would lead
to some nested MI output, not so great.
There is probably still a chance to have bad MI output, if
sigchld_handler is invoked in the middle of mi_console_file's flush, and
the line being flushed is only partially sent to m_raw. The solution
would probably be to block signals during flushing. Since this is only
used for debug output, I don't know if it's worth the effort to do that.
To implement write_async_safe, I needed to use the fputstrn_unfiltered,
which does the necessary escaping (e.g. replace \n with \\n). I started
by adding printchar's callback parameters to fputstrn_unfiltered, to be
able to pass async-safe versions of them. It's not easy to provide an
async-safe version of do_fprintf, but it turns out that we can easily
replace printchar's callbacks with a single do_fputc quite easily. The
async-safe version of do_fputc simply calls the underlying ui_file's
write_async_safe method.
gdb/ChangeLog:
PR mi/22299
* mi/mi-console.c (do_fputc_async_safe): New.
(mi_console_file::write_async_safe): New.
(mi_console_file::flush): Adjust calls to fputstrn_unfiltered.
* mi/mi-console.h (class mi_console_file) <write_async_safe>:
New.
* ui-file.c (ui_file::putstrn): Adjust call to
fputstrn_unfiltered.
* utils.c (printchar): Replace do_fputs and do_fprintf
parameters by do_fputc.
(fputstr_filtered): Adjust call to printchar.
(fputstr_unfiltered): Likewise.
(fputstrn_filtered): Likewise.
(fputstrn_unfiltered): Add do_fputc parameter, pass to
printchar.
* utils.h (do_fputc_ftype): New typedef.
(fputstrn_unfiltered): Add do_fputc parameter.
59 lines
1.7 KiB
C++
59 lines
1.7 KiB
C++
/* MI Command Set - MI Console.
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Copyright (C) 2000-2018 Free Software Foundation, Inc.
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Contributed by Cygnus Solutions (a Red Hat company).
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef MI_CONSOLE_H
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#define MI_CONSOLE_H
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/* An output stream for MI. Wraps a given output stream with a prefix
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and handles quoting. This stream is locally buffered. */
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class mi_console_file : public ui_file
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{
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public:
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/* Create a console that wraps the given output stream RAW with the
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string PREFIX and quoting it with QUOTE. */
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mi_console_file (ui_file *raw, const char *prefix, char quote);
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/* MI-specific API. */
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void set_raw (ui_file *raw);
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/* ui_file-specific methods. */
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void flush () override;
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void write (const char *buf, long length_buf) override;
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void write_async_safe (const char *buf, long length_buf) override;
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private:
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/* The wrapped raw output stream. */
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ui_file *m_raw;
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/* The local buffer. */
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string_file m_buffer;
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/* The prefix. */
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const char *m_prefix;
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/* The quote char. */
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char m_quote;
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};
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#endif
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