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Commit5c7038d

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Refactor pipe_read_line to return the full line
Commit5b2f4af refactored find_other_exec() and in the processcreated pipe_read_line() into a static routine for reading a singleline of output, aimed at reading version numbers. Commita7e8ecelater exposed it externally in order to read a postgresql.conf GUCusing "postgres -C ..". Further,f06b1c5 also made use of it forreading a version string much like find_other_exec(). The internalvariable remained "pgver", even when used for other purposes.Since the function requires passing a buffer and its size, and atmost size - 1 bytes will be read via fgets(), there is a truncationrisk when using this for reading GUCs (like how pg_rewind does,though the risk in this case is marginal).To keep this as generic functionality for reading a line from a pipe,this refactors pipe_read_line() into returning an allocated buffercontaining all of the line to remove the risk of silent truncation.Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>Reviewed-by: John Naylor <johncnaylorls@gmail.com>Discussion:https://postgr.es/m/DEDF73CE-D528-49A3-9089-B3592FD671A9@yesql.se
1 parentc01f6ef commit5c7038d

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4 files changed

+36
-25
lines changed

4 files changed

+36
-25
lines changed

‎src/bin/pg_rewind/pg_rewind.c

Lines changed: 6 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -1055,8 +1055,7 @@ static void
10551055
getRestoreCommand(constchar*argv0)
10561056
{
10571057
intrc;
1058-
charpostgres_exec_path[MAXPGPATH],
1059-
cmd_output[MAXPGPATH];
1058+
charpostgres_exec_path[MAXPGPATH];
10601059
PQExpBufferpostgres_cmd;
10611060

10621061
if (!restore_wal)
@@ -1105,16 +1104,15 @@ getRestoreCommand(const char *argv0)
11051104
/* add -C switch, for restore_command */
11061105
appendPQExpBufferStr(postgres_cmd," -C restore_command");
11071106

1108-
if (!pipe_read_line(postgres_cmd->data,cmd_output,sizeof(cmd_output)))
1109-
exit(1);
1107+
restore_command=pipe_read_line(postgres_cmd->data);
1108+
if (restore_command==NULL)
1109+
pg_fatal("unable to read restore_command from target cluster");
11101110

1111-
(void)pg_strip_crlf(cmd_output);
1111+
(void)pg_strip_crlf(restore_command);
11121112

1113-
if (strcmp(cmd_output,"")==0)
1113+
if (strcmp(restore_command,"")==0)
11141114
pg_fatal("restore_command is not set in the target cluster");
11151115

1116-
restore_command=pg_strdup(cmd_output);
1117-
11181116
pg_log_debug("using for rewind restore_command = \'%s\'",
11191117
restore_command);
11201118

‎src/bin/pg_upgrade/exec.c

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -431,7 +431,7 @@ static void
431431
check_exec(constchar*dir,constchar*program,boolcheck_version)
432432
{
433433
charpath[MAXPGPATH];
434-
charline[MAXPGPATH];
434+
char*line;
435435
charcmd[MAXPGPATH];
436436
charversionstr[128];
437437

@@ -442,7 +442,7 @@ check_exec(const char *dir, const char *program, bool check_version)
442442

443443
snprintf(cmd,sizeof(cmd),"\"%s\" -V",path);
444444

445-
if (!pipe_read_line(cmd,line,sizeof(line)))
445+
if ((line=pipe_read_line(cmd))==NULL)
446446
pg_fatal("check for \"%s\" failed: cannot execute",
447447
path);
448448

@@ -456,4 +456,6 @@ check_exec(const char *dir, const char *program, bool check_version)
456456
pg_fatal("check for \"%s\" failed: incorrect version: found \"%s\", expected \"%s\"",
457457
path,line,versionstr);
458458
}
459+
460+
pg_free(line);
459461
}

‎src/common/exec.c

Lines changed: 25 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -42,6 +42,8 @@
4242
#endif
4343
#endif
4444

45+
#include"common/string.h"
46+
4547
/* Inhibit mingw CRT's auto-globbing of command line arguments */
4648
#if defined(WIN32)&& !defined(_MSC_VER)
4749
externint_CRT_glob=0;/* 0 turns off globbing; 1 turns it on */
@@ -328,7 +330,7 @@ find_other_exec(const char *argv0, const char *target,
328330
constchar*versionstr,char*retpath)
329331
{
330332
charcmd[MAXPGPATH];
331-
charline[MAXPGPATH];
333+
char*line;
332334

333335
if (find_my_exec(argv0,retpath)<0)
334336
return-1;
@@ -346,46 +348,55 @@ find_other_exec(const char *argv0, const char *target,
346348

347349
snprintf(cmd,sizeof(cmd),"\"%s\" -V",retpath);
348350

349-
if (!pipe_read_line(cmd,line,sizeof(line)))
351+
if ((line=pipe_read_line(cmd))==NULL)
350352
return-1;
351353

352354
if (strcmp(line,versionstr)!=0)
355+
{
356+
pfree(line);
353357
return-2;
358+
}
354359

360+
pfree(line);
355361
return0;
356362
}
357363

358364

359365
/*
360-
* Execute a command in a pipe and read the first line from it.
366+
* Execute a command in a pipe and read the first line from it. The returned
367+
* string is palloc'd (malloc'd in frontend code), the caller is responsible
368+
* for freeing.
361369
*/
362370
char*
363-
pipe_read_line(char*cmd,char*line,intmaxsize)
371+
pipe_read_line(char*cmd)
364372
{
365-
FILE*pgver;
373+
FILE*pipe_cmd;
374+
char*line;
366375

367376
fflush(NULL);
368377

369378
errno=0;
370-
if ((pgver=popen(cmd,"r"))==NULL)
379+
if ((pipe_cmd=popen(cmd,"r"))==NULL)
371380
{
372381
perror("popen failure");
373382
returnNULL;
374383
}
375384

385+
/* Make sure popen() didn't change errno */
376386
errno=0;
377-
if (fgets(line,maxsize,pgver)==NULL)
387+
line=pg_get_line(pipe_cmd,NULL);
388+
389+
if (line==NULL)
378390
{
379-
if (feof(pgver))
380-
fprintf(stderr,"no data was returned by command \"%s\"\n",cmd);
391+
if (ferror(pipe_cmd))
392+
log_error(errcode_for_file_access(),
393+
_("could not read from command \"%s\": %m"),cmd);
381394
else
382-
perror("fgets failure");
383-
pclose(pgver);/* no error checking */
384-
returnNULL;
395+
log_error(errcode_for_file_access(),
396+
_("no data was returned by command \"%s\": %m"),cmd);
385397
}
386398

387-
if (pclose_check(pgver))
388-
returnNULL;
399+
(void)pclose_check(pipe_cmd);
389400

390401
returnline;
391402
}

‎src/include/port.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -137,7 +137,7 @@ extern intvalidate_exec(const char *path);
137137
externintfind_my_exec(constchar*argv0,char*retpath);
138138
externintfind_other_exec(constchar*argv0,constchar*target,
139139
constchar*versionstr,char*retpath);
140-
externchar*pipe_read_line(char*cmd,char*line,intmaxsize);
140+
externchar*pipe_read_line(char*cmd);
141141

142142
/* Doesn't belong here, but this is used with find_other_exec(), so... */
143143
#definePG_BACKEND_VERSIONSTR "postgres (PostgreSQL) " PG_VERSION "\n"

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