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Simon Marchi 7c4e78cf63 Implement write_async_safe for mi_console_file (PR 22299)
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.
2018-04-07 13:48:06 -04:00
bfd Automatic date update in version.in 2018-04-07 00:00:25 +00:00
binutils Display all DWARF 5 language names 2018-04-06 10:58:34 -06:00
config config: Sync with GCC 2018-04-05 15:22:13 -07:00
cpu
elfcpp Add support for R_AARCH64_TLSLE_LDST8_TPREL_LO12, etc. 2018-03-28 09:10:25 -07:00
etc
gas Use dlsym to check if libdl is needed for plugin 2018-04-05 15:31:53 -07:00
gdb Implement write_async_safe for mi_console_file (PR 22299) 2018-04-07 13:48:06 -04:00
gold Further improve warnings for relocations referring to discarded sections. 2018-04-06 22:50:14 -07:00
gprof Use dlsym to check if libdl is needed for plugin 2018-04-05 15:31:53 -07:00
include [1/2][GAS][AARCH64]Add BFD_RELOC_AARCH64_TLSLE_LDST8/16/32/64_TPREL_LO12 support in GAS. 2018-03-28 18:03:55 +01:00
intl
ld Use dlsym to check if libdl is needed for plugin 2018-04-05 15:31:53 -07:00
libdecnumber
libiberty
opcodes i386: Clear vex instead of vex.evex 2018-04-04 04:36:44 -07:00
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		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
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	make

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	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
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