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Revision 05d1ed6148305d299693000856e4971e9f642662 authored by Ben Wijen on 22 August 2016, 12:47:55 UTC, committed by Junio C Hamano on 23 August 2016, 16:09:55 UTC 
mingw: ensure temporary file handles are not inherited by child processes
 
When the index is locked and child processes inherit the handle to
said lock and the parent process wants to remove the lock before the
child process exits, on Windows there is a problem: it won't work
because files cannot be deleted if a process holds a handle on them.
The symptom:

    Rename from 'xxx/.git/index.lock' to 'xxx/.git/index' failed.
    Should I try again? (y/n)

Spawning child processes with bInheritHandles==FALSE would not work
because no file handles would be inherited, not even the hStdXxx
handles in STARTUPINFO (stdin/stdout/stderr).

Opening every file with O_NOINHERIT does not work, either, as e.g.
git-upload-pack expects inherited file handles.

This leaves us with the only way out: creating temp files with the
O_NOINHERIT flag. This flag is Windows-specific, however. For our
purposes, it is equivalent to O_CLOEXEC (which does not exist on
Windows), so let's just open temporary files with the O_CLOEXEC flag and
map that flag to O_NOINHERIT on Windows.

As Eric Wong pointed out, we need to be careful to handle the case where
the Linux headers used to compile Git support O_CLOEXEC but the Linux
kernel used to run Git does not: it returns an EINVAL.

This fixes the test that we just introduced to demonstrate the problem.

Signed-off-by: Ben Wijen <ben@wijen.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Raw File
help.h 
#ifndef HELP_H
#define HELP_H

struct cmdnames {
	int alloc;
	int cnt;
	struct cmdname {
		size_t len; /* also used for similarity index in help.c */
		char name[FLEX_ARRAY];
	} **names;
};

static inline void mput_char(char c, unsigned int num)
{
	while(num--)
		putchar(c);
}

extern void list_common_cmds_help(void);
extern const char *help_unknown_cmd(const char *cmd);
extern void load_command_list(const char *prefix,
			      struct cmdnames *main_cmds,
			      struct cmdnames *other_cmds);
extern void add_cmdname(struct cmdnames *cmds, const char *name, int len);
/* Here we require that excludes is a sorted list. */
extern void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes);
extern int is_in_cmdlist(struct cmdnames *cmds, const char *name);
extern void list_commands(unsigned int colopts, struct cmdnames *main_cmds, struct cmdnames *other_cmds);

/*
 * call this to die(), when it is suspected that the user mistyped a
 * ref to the command, to give suggested "correct" refs.
 */
extern void help_unknown_ref(const char *ref, const char *cmd, const char *error);
#endif /* HELP_H */
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