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Merge pull request #91 from jonnysoe/pid_tempname 

Fix runtime error upon multiple flex processes
This commit is contained in:
Simon Sobisch 2023-03-05 21:15:56 +01:00 committed by GitHub
parent 9118533590 2bfaf44a53
commit 300f48ba3e
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GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 55 additions and 26 deletions
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13
bison/src/output.c
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@ -44,6 +44,7 @@
#include "scan-skel.h"
#include "symtab.h"
#include "tables.h"
#include "pid_tempname.h"
#include "strversion.h"
static struct obstack format_obstack;
@ -727,7 +728,7 @@ output_skeleton (void)
{
FILE *m4_in = NULL;
FILE *m4_out = NULL;
char m4_in_file_name[/*MAX_PATH*/260];
char m4_in_file_name[/*MAX_PATH*/260];
char m4_out_file_name[/*MAX_PATH*/260];
char const *argv[11];
@ -813,10 +814,7 @@ output_skeleton (void)
if (trace_flag & trace_muscles)
muscles_output (stderr);
{
char* p = _tempnam(NULL, "~m4_in_");
if (!p)
error (EXIT_FAILURE, get_errno (),
"_tempnam");
char* p = pid_tempname("~m4_in_");
m4_in = fopen(strcpy(m4_in_file_name, p), "wb+");
if (!m4_in)
error (EXIT_FAILURE, get_errno (),
@ -832,10 +830,7 @@ output_skeleton (void)
/* Read and process m4's output. */
timevar_push (tv_m4);
{
char *p = _tempnam(NULL, "~m4_out_");
if (!m4_out_file_name)
error (EXIT_FAILURE, get_errno (),
"_tempnam");
char *p = pid_tempname("~m4_out_");
m4_out = fopen(strcpy(m4_out_file_name, p), "wb+");
if (!m4_out)
error (EXIT_FAILURE, get_errno (),

39
common/misc/pid_tempname.c Normal file
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@ -0,0 +1,39 @@
#include "pid_tempname.h"
#include <stdio.h>
#include <process.h>
char temp_prefix[40];
// This adds the unique process id to the built in _tempnam to prevent race condition
// This race condition is more prevalent in Ninja as it parallelizes build and instantiates multiple win_flex/win_bison
// flex_temp_out_main fails frequently as its used for a longer time (compared to temp_file_names),
// hence more possibility to overlap
const char *pid_tempname (const char *prefix)
{
// Here is the race condition:
//
// flex A
// | flex B
// ↓ |
// _tempnam returns ~file_X ↓
// | _tempnam returns ~file_X
// ↓ |
// freopen ~file_X w+ ↓
// | freopen ~file_X w+
// ↓ |
// ... ↓
// | ...
// ↓ |
// _unlink ~file_X ... <- Fails to print
// ↓
// _unlink ~file_X <- Fails to delete
//
// It is also possible that ~file_X was deleted before the lagging win_flex is done, which can cause other errors,
// hence changing to non-fatal error upon missing ~file_X on _unlink will not work all the time
// This problem can be prevented with an even more unique temporary file name by adding the current process ID
// Synchronization is not necessary either as there is no reason for the independent processes to wait...
// The reason why this is an issue is because Windows filesystem is reflected immediately,
// unlike inode in Linux that only properly deletes files when their link count is down to zero
sprintf(temp_prefix, "%s%d_", prefix, _getpid());
return _tempnam(NULL, temp_prefix);
}

4
common/misc/pid_tempname.h Normal file
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@ -0,0 +1,4 @@
// The longer pid_tempname was used to distinguish from GNU's tempname header
///@brief Generates a unique pid temporary file
const char *pid_tempname (const char *prefix);

7
flex/src/filter.c
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@ -22,6 +22,7 @@
/* PURPOSE. */
#include "flexdef.h"
#include "pid_tempname.h"
static const char * check_4_gnu_m4 =
"m4_dnl ifdef(`__gnu__', ,"
"`errprint(Flex requires GNU M4. Set the PATH or set the M4 environment variable to its path name.)"
@ -75,9 +76,7 @@ FILE* mkstempFILE (char *pref, const char *mode)
if (!pref || !*pref)
return NULL;
name = _tempnam(flex_tmp_dir, pref);
if (!name)
return NULL;
name = pid_tempname(pref);
fd = fopen(name, mode);
if (fd)
@ -255,7 +254,7 @@ bool filter_apply_chain (struct filter * chain, FILE* in_file, FILE* out_file)
}
return result;
#if 0
#if 0
int pid, pipes[2];

1
flex/src/flexdef.h
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@ -1136,7 +1136,6 @@ extern int filter_tee_header(struct filter *chain);
extern int filter_fix_linedirs(struct filter *chain);
extern int filter_m4_p(struct filter *chain);
extern const char* flex_tmp_dir;
extern FILE* mkstempFILE(char *pref, const char *mode);
extern void unlinktemp();

17
flex/src/main.c
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@ -36,6 +36,7 @@
//#include "version.h"
#include "options.h"
#include "tables.h"
#include "pid_tempname.h"
#include "parse.h"
#include <io.h>
#include <fcntl.h>
@ -411,12 +412,14 @@ void check_options (void)
*/
/* collect all output to temp file to use it as input for filter chain */
prev_stdout = _dup(1); // prev_stdout now refers to "stdout"
prev_stdout = _dup(1); // prev_stdout now refers to "stdout"
flex_temp_out_main = _strdup(pid_tempname("~flex_out_main_"));
freopen(flex_temp_out_main, "w+", stdout);
if (stdout == NULL)
lerr(_("could not create %s"), flex_temp_out_main);
yyout = stdout;
@ -1039,8 +1042,6 @@ void flexend (int exit_status)
/* flexinit - initialize flex */
const char* flex_tmp_dir;
void flexinit (int argc, char **argv)
{
int i, sawcmpflag, rv, optind;
@ -1048,14 +1049,6 @@ void flexinit (int argc, char **argv)
scanopt_t sopt;
char *ext_path = 0;
flex_tmp_dir = getenv ("FLEX_TMP_DIR");
{
char *p = _tempnam(flex_tmp_dir, "~flex_out_main_");
if (!p)
flexfatal(_("_tempnam(main)"));
flex_temp_out_main = _strdup(p);
}
printstats = syntaxerror = trace = spprdflt = false;
lex_compat = posix_compat = C_plus_plus = backing_up_report =
ddebug = fulltbl = false;