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Fix the problem in popen that makes correct vfork semantics fail.

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Specifically, popen modifies a variable "pdes[1]" in the child
in such a way that it breaks code in the parent (due to the address
space sharing.)
This commit is contained in:
John Dyson 1997-04-16 03:26:50 +00:00
parent 93d71a483c
commit 1174d9f9df
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=24975
1 changed files with 11 additions and 6 deletions
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17
lib/libc/gen/popen.c
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@ -93,14 +93,19 @@ popen(command, type)
/* NOTREACHED */ /* NOTREACHED */
case 0: /* Child. */ case 0: /* Child. */
if (*type == 'r') { if (*type == 'r') {
if (pdes[1] != STDOUT_FILENO) { /*
(void)dup2(pdes[1], STDOUT_FILENO); * We must NOT modify pdes, due to the
(void)close(pdes[1]); * semantics of vfork.
pdes[1] = STDOUT_FILENO; */
int tpdes1 = pdes[1];
if (tpdes1 != STDOUT_FILENO) {
(void)dup2(tpdes1, STDOUT_FILENO);
(void)close(tpdes1);
tpdes1 = STDOUT_FILENO;
} }
(void) close(pdes[0]); (void) close(pdes[0]);
if (twoway && (pdes[1] != STDIN_FILENO)) if (twoway && (tpdes1 != STDIN_FILENO))
(void)dup2(pdes[1], STDIN_FILENO); (void)dup2(tpdes1, STDIN_FILENO);
} else { } else {
if (pdes[0] != STDIN_FILENO) { if (pdes[0] != STDIN_FILENO) {
(void)dup2(pdes[0], STDIN_FILENO); (void)dup2(pdes[0], STDIN_FILENO);