Reimplement popen(3)/pclose(3).

pclose(3) is now an alias for fclose(3). We could add a FORTIFY check
that you use pclose(3) if and only if you used popen(3), but there seems
little value to that when we can just do the right thing.

This patch also adds the missing locking to _fwalk --- we need to lock
both the global list of FILE*s and also each FILE* we touch. POSIX says
that "The popen() function shall ensure that any streams from previous
popen() calls that remain open in the parent process are closed in the
new child process", which we implement via _fwalk(fclose) in the child,
but we might want to just make *all* popen(3) file descriptors O_CLOEXEC
in all cases.

Ignore fewer errors in popen(3) failure cases.

Improve popen(3) test coverage.

Bug: http://b/72470344
Test: ran tests
Change-Id: Ic937594bf28ec88b375f7e5825b9c05f500af438

1 files changed, 59 insertions, 1 deletions

diff --git a/tests/stdio_test.cpp b/tests/stdio_test.cpp
index 33514d4ff..6282ec3cc 100644
--- a/tests/stdio_test.cpp
+++ b/tests/stdio_test.cpp
@@ -22,6 +22,7 @@
 #include <math.h>
 #include <stdio.h>
 #include <sys/types.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <wchar.h>
@@ -888,7 +889,7 @@ TEST(STDIO_TEST, fprintf_failures_7229520) {
   ASSERT_EQ(-1, fclose(fp));
 }
 
-TEST(STDIO_TEST, popen) {
+TEST(STDIO_TEST, popen_r) {
   FILE* fp = popen("cat /proc/version", "r");
   ASSERT_TRUE(fp != NULL);
 
@@ -900,6 +901,63 @@ TEST(STDIO_TEST, popen) {
   ASSERT_EQ(0, pclose(fp));
 }
 
+TEST(STDIO_TEST, popen_socketpair) {
+  FILE* fp = popen("cat", "r+");
+  ASSERT_TRUE(fp != NULL);
+
+  fputs("hello\nworld\n", fp);
+  fflush(fp);
+
+  char buf[16];
+  ASSERT_NE(nullptr, fgets(buf, sizeof(buf), fp));
+  EXPECT_STREQ("hello\n", buf);
+  ASSERT_NE(nullptr, fgets(buf, sizeof(buf), fp));
+  EXPECT_STREQ("world\n", buf);
+
+  ASSERT_EQ(0, pclose(fp));
+}
+
+TEST(STDIO_TEST, popen_socketpair_shutdown) {
+  FILE* fp = popen("uniq -c", "r+");
+  ASSERT_TRUE(fp != NULL);
+
+  fputs("a\na\na\na\nb\n", fp);
+  fflush(fp);
+  ASSERT_EQ(0, shutdown(fileno(fp), SHUT_WR));
+
+  char buf[16];
+  ASSERT_NE(nullptr, fgets(buf, sizeof(buf), fp));
+  EXPECT_STREQ("      4 a\n", buf);
+  ASSERT_NE(nullptr, fgets(buf, sizeof(buf), fp));
+  EXPECT_STREQ("      1 b\n", buf);
+
+  ASSERT_EQ(0, pclose(fp));
+}
+
+TEST(STDIO_TEST, popen_return_value_0) {
+  FILE* fp = popen("true", "r");
+  ASSERT_TRUE(fp != NULL);
+  int status = pclose(fp);
+  EXPECT_TRUE(WIFEXITED(status));
+  EXPECT_EQ(0, WEXITSTATUS(status));
+}
+
+TEST(STDIO_TEST, popen_return_value_1) {
+  FILE* fp = popen("false", "r");
+  ASSERT_TRUE(fp != NULL);
+  int status = pclose(fp);
+  EXPECT_TRUE(WIFEXITED(status));
+  EXPECT_EQ(1, WEXITSTATUS(status));
+}
+
+TEST(STDIO_TEST, popen_return_value_signal) {
+  FILE* fp = popen("kill -7 $$", "r");
+  ASSERT_TRUE(fp != NULL);
+  int status = pclose(fp);
+  EXPECT_TRUE(WIFSIGNALED(status));
+  EXPECT_EQ(7, WTERMSIG(status));
+}
+
 TEST(STDIO_TEST, getc) {
   FILE* fp = fopen("/proc/version", "r");
   ASSERT_TRUE(fp != NULL);