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5a17353c DD |
1 | /* Utilities to execute a program in a subprocess (possibly linked by pipes |
2 | with other subprocesses), and wait for it. Generic Unix version | |
3 | (also used for UWIN and VMS). | |
1e45deed | 4 | Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004, 2005 |
5a17353c DD |
5 | Free Software Foundation, Inc. |
6 | ||
7 | This file is part of the libiberty library. | |
8 | Libiberty is free software; you can redistribute it and/or | |
9 | modify it under the terms of the GNU Library General Public | |
10 | License as published by the Free Software Foundation; either | |
11 | version 2 of the License, or (at your option) any later version. | |
12 | ||
13 | Libiberty is distributed in the hope that it will be useful, | |
14 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Library General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Library General Public | |
19 | License along with libiberty; see the file COPYING.LIB. If not, | |
20 | write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
21 | Boston, MA 02111-1307, USA. */ | |
22 | ||
23 | #include "pex-common.h" | |
24 | ||
25 | #include <stdio.h> | |
26 | #include <errno.h> | |
27 | #ifdef NEED_DECLARATION_ERRNO | |
28 | extern int errno; | |
29 | #endif | |
30 | #ifdef HAVE_STRING_H | |
31 | #include <string.h> | |
32 | #endif | |
33 | #ifdef HAVE_UNISTD_H | |
34 | #include <unistd.h> | |
35 | #endif | |
36 | #ifdef HAVE_STDLIB_H | |
37 | #include <stdlib.h> | |
38 | #endif | |
39 | #ifdef HAVE_SYS_WAIT_H | |
40 | #include <sys/wait.h> | |
41 | #endif | |
42 | ||
43 | #ifndef HAVE_WAITPID | |
44 | #define waitpid(pid, status, flags) wait(status) | |
45 | #endif | |
46 | ||
12a7367e DD |
47 | #ifdef vfork /* Autoconf may define this to fork for us. */ |
48 | # define VFORK_STRING "fork" | |
49 | #else | |
50 | # define VFORK_STRING "vfork" | |
51 | #endif | |
52 | #ifdef HAVE_VFORK_H | |
53 | #include <vfork.h> | |
54 | #endif | |
55 | #ifdef VMS | |
56 | #define vfork() (decc$$alloc_vfork_blocks() >= 0 ? \ | |
57 | lib$get_current_invo_context(decc$$get_vfork_jmpbuf()) : -1) | |
58 | #endif /* VMS */ | |
59 | ||
60 | /* Execute a program, possibly setting up pipes to programs executed | |
61 | via other calls to this function. | |
62 | ||
63 | This version of the function uses vfork. In general vfork is | |
70615d15 | 64 | similar to setjmp/longjmp, in that any variable which is modified by |
12a7367e DD |
65 | the child process has an indeterminate value in the parent process. |
66 | We follow a safe approach here by not modifying any variables at | |
67 | all in the child process (with the possible exception of variables | |
68 | modified by xstrerror if exec fails, but this is unlikely to be | |
69 | detectable). | |
70 | ||
71 | We work a little bit harder to avoid gcc warnings. gcc will warn | |
72 | about any automatic variable which is live at the time of the | |
73 | vfork, which is non-volatile, and which is either set more than | |
74 | once or is an argument to the function. This warning isn't quite | |
75 | right, since what we really care about is whether the variable is | |
76 | live at the time of the vfork and set afterward by the child | |
77 | process, but gcc only checks whether the variable is set more than | |
78 | once. To avoid this warning, we ensure that any variable which is | |
79 | live at the time of the vfork (i.e., used after the vfork) is set | |
80 | exactly once and is not an argument, or is marked volatile. */ | |
5a17353c DD |
81 | |
82 | int | |
1e45deed DD |
83 | pexecute (const char *program, char * const *argv, const char *this_pname, |
84 | const char *temp_base ATTRIBUTE_UNUSED, | |
85 | char **errmsg_fmt, char **errmsg_arg, int flagsarg) | |
5a17353c | 86 | { |
5a17353c DD |
87 | int pid; |
88 | int pdes[2]; | |
12a7367e | 89 | int out; |
5a17353c | 90 | int input_desc, output_desc; |
12a7367e DD |
91 | int flags; |
92 | /* We declare these to be volatile to avoid warnings from gcc about | |
93 | them being clobbered by vfork. */ | |
94 | volatile int retries, sleep_interval; | |
5a17353c DD |
95 | /* Pipe waiting from last process, to be used as input for the next one. |
96 | Value is STDIN_FILE_NO if no pipe is waiting | |
97 | (i.e. the next command is the first of a group). */ | |
98 | static int last_pipe_input; | |
99 | ||
12a7367e DD |
100 | flags = flagsarg; |
101 | ||
5a17353c DD |
102 | /* If this is the first process, initialize. */ |
103 | if (flags & PEXECUTE_FIRST) | |
104 | last_pipe_input = STDIN_FILE_NO; | |
105 | ||
106 | input_desc = last_pipe_input; | |
107 | ||
108 | /* If this isn't the last process, make a pipe for its output, | |
109 | and record it as waiting to be the input to the next process. */ | |
110 | if (! (flags & PEXECUTE_LAST)) | |
111 | { | |
112 | if (pipe (pdes) < 0) | |
113 | { | |
114 | *errmsg_fmt = "pipe"; | |
115 | *errmsg_arg = NULL; | |
116 | return -1; | |
117 | } | |
12a7367e | 118 | out = pdes[WRITE_PORT]; |
5a17353c DD |
119 | last_pipe_input = pdes[READ_PORT]; |
120 | } | |
121 | else | |
122 | { | |
123 | /* Last process. */ | |
12a7367e | 124 | out = STDOUT_FILE_NO; |
5a17353c DD |
125 | last_pipe_input = STDIN_FILE_NO; |
126 | } | |
127 | ||
12a7367e DD |
128 | output_desc = out; |
129 | ||
5a17353c DD |
130 | /* Fork a subprocess; wait and retry if it fails. */ |
131 | sleep_interval = 1; | |
132 | pid = -1; | |
133 | for (retries = 0; retries < 4; retries++) | |
134 | { | |
12a7367e | 135 | pid = vfork (); |
5a17353c DD |
136 | if (pid >= 0) |
137 | break; | |
138 | sleep (sleep_interval); | |
139 | sleep_interval *= 2; | |
140 | } | |
141 | ||
142 | switch (pid) | |
143 | { | |
144 | case -1: | |
145 | *errmsg_fmt = "fork"; | |
146 | *errmsg_arg = NULL; | |
147 | return -1; | |
148 | ||
149 | case 0: /* child */ | |
150 | /* Move the input and output pipes into place, if necessary. */ | |
151 | if (input_desc != STDIN_FILE_NO) | |
152 | { | |
153 | close (STDIN_FILE_NO); | |
154 | dup (input_desc); | |
155 | close (input_desc); | |
156 | } | |
157 | if (output_desc != STDOUT_FILE_NO) | |
158 | { | |
159 | close (STDOUT_FILE_NO); | |
160 | dup (output_desc); | |
161 | close (output_desc); | |
162 | } | |
163 | ||
164 | /* Close the parent's descs that aren't wanted here. */ | |
165 | if (last_pipe_input != STDIN_FILE_NO) | |
166 | close (last_pipe_input); | |
167 | ||
168 | /* Exec the program. */ | |
12a7367e DD |
169 | if (flags & PEXECUTE_SEARCH) |
170 | execvp (program, argv); | |
171 | else | |
172 | execv (program, argv); | |
173 | ||
174 | /* We don't want to call fprintf after vfork. */ | |
175 | #define writeerr(s) write (STDERR_FILE_NO, s, strlen (s)) | |
176 | writeerr (this_pname); | |
177 | writeerr (": "); | |
178 | writeerr ("installation problem, cannot exec '"); | |
179 | writeerr (program); | |
180 | writeerr ("': "); | |
181 | writeerr (xstrerror (errno)); | |
182 | writeerr ("\n"); | |
183 | _exit (-1); | |
5a17353c DD |
184 | /* NOTREACHED */ |
185 | return 0; | |
186 | ||
187 | default: | |
188 | /* In the parent, after forking. | |
189 | Close the descriptors that we made for this child. */ | |
190 | if (input_desc != STDIN_FILE_NO) | |
191 | close (input_desc); | |
192 | if (output_desc != STDOUT_FILE_NO) | |
193 | close (output_desc); | |
194 | ||
195 | /* Return child's process number. */ | |
196 | return pid; | |
197 | } | |
198 | } | |
199 | ||
200 | int | |
1e45deed | 201 | pwait (int pid, int *status, int flags ATTRIBUTE_UNUSED) |
5a17353c DD |
202 | { |
203 | /* ??? Here's an opportunity to canonicalize the values in STATUS. | |
204 | Needed? */ | |
205 | pid = waitpid (pid, status, 0); | |
206 | return pid; | |
207 | } |