Develop Reference

Calling ffmpeg.c's main twice causes app crash

Using FFmpeg 4.0.2 and call its ffmpeg.c's main function twice causes Android app crash (using FFmpeg shared libs and JNI)
A/libc: Fatal signal 11 (SIGSEGV), code 1, fault addr 0x0 in tid 20153
Though it works ok for FFmpeg 3.2.5
FFmpeg 4.0.2 main
int main(int argc, char **argv) {
int i, ret;
int64_t ti;
init_dynload();
register_exit(ffmpeg_cleanup);
setvbuf(stderr,NULL,_IONBF,0); /* win32 runtime needs this */
av_log_set_flags(AV_LOG_SKIP_REPEATED);
parse_loglevel(argc, argv, options);
if(argc>1 && !strcmp(argv[1], "-d")){
run_as_daemon=1;
av_log_set_callback(log_callback_null);
argc--;
argv++;
}
#if CONFIG_AVDEVICE
avdevice_register_all();
#endif
avformat_network_init();
show_banner(argc, argv, options);
/* parse options and open all input/output files */
ret = ffmpeg_parse_options(argc, argv);
if (ret < 0)
exit_program(1);
if (nb_output_files <= 0 && nb_input_files == 0) {
show_usage();
av_log(NULL, AV_LOG_WARNING, "Use -h to get full help or, even better, run 'man %s'\n", program_name);
exit_program(1);
}
/* file converter / grab */
if (nb_output_files <= 0) {
av_log(NULL, AV_LOG_FATAL, "At least one output file must be specified\n");
exit_program(1);
}
// if (nb_input_files == 0) {
// av_log(NULL, AV_LOG_FATAL, "At least one input file must be specified\n");
// exit_program(1);
// }
for (i = 0; i < nb_output_files; i++) {
if (strcmp(output_files[i]->ctx->oformat->name, "rtp"))
want_sdp = 0;
}
current_time = ti = getutime();
if (transcode() < 0)
exit_program(1);
ti = getutime() - ti;
if (do_benchmark) {
av_log(NULL, AV_LOG_INFO, "bench: utime=%0.3fs\n", ti / 1000000.0);
}
av_log(NULL, AV_LOG_DEBUG, "%"PRIu64" frames successfully decoded, %"PRIu64" decoding errors\n",
decode_error_stat[0], decode_error_stat[1]);
if ((decode_error_stat[0] + decode_error_stat[1]) * max_error_rate < decode_error_stat[1])
exit_program(69);
ffmpeg_cleanup(received_nb_signals ? 255 : main_return_code);
return main_return_code;
}
FFmpeg 3.2.5 main
int main(int argc, char **argv) {
av_log(NULL, AV_LOG_WARNING, " Command start");
int i, ret;
int64_t ti;
init_dynload();
register_exit(ffmpeg_cleanup);
setvbuf(stderr, NULL, _IONBF, 0); /* win32 runtime needs this */
av_log_set_flags(AV_LOG_SKIP_REPEATED);
parse_loglevel(argc, argv, options);
if (argc > 1 && !strcmp(argv[1], "-d")) {
run_as_daemon = 1;
av_log_set_callback(log_callback_null);
argc--;
argv++;
}
avcodec_register_all();
#if CONFIG_AVDEVICE
avdevice_register_all();
#endif
avfilter_register_all();
av_register_all();
avformat_network_init();
av_log(NULL, AV_LOG_WARNING, " Register to complete the codec");
show_banner(argc, argv, options);
/* parse options and open all input/output files */
ret = ffmpeg_parse_options(argc, argv);
if (ret < 0)
exit_program(1);
if (nb_output_files <= 0 && nb_input_files == 0) {
show_usage();
av_log(NULL, AV_LOG_WARNING, "Use -h to get full help or, even better, run 'man %s'\n",
program_name);
exit_program(1);
}
/* file converter / grab */
if (nb_output_files <= 0) {
av_log(NULL, AV_LOG_FATAL, "At least one output file must be specified\n");
exit_program(1);
}
// if (nb_input_files == 0) {
// av_log(NULL, AV_LOG_FATAL, "At least one input file must be specified\n");
// exit_program(1);
// }
for (i = 0; i < nb_output_files; i++) {
if (strcmp(output_files[i]->ctx->oformat->name, "rtp"))
want_sdp = 0;
}
current_time = ti = getutime();
if (transcode() < 0)
exit_program(1);
ti = getutime() - ti;
if (do_benchmark) {
av_log(NULL, AV_LOG_INFO, "bench: utime=%0.3fs\n", ti / 1000000.0);
}
av_log(NULL, AV_LOG_DEBUG, "%"PRIu64" frames successfully decoded, %"PRIu64" decoding errors\n",
decode_error_stat[0], decode_error_stat[1]);
if ((decode_error_stat[0] + decode_error_stat[1]) * max_error_rate < decode_error_stat[1])
exit_program(69);
exit_program(received_nb_signals ? 255 : main_return_code);
nb_filtergraphs = 0;
nb_input_streams = 0;
nb_input_files = 0;
progress_avio = NULL;
input_streams = NULL;
nb_input_streams = 0;
input_files = NULL;
nb_input_files = 0;
output_streams = NULL;
nb_output_streams = 0;
output_files = NULL;
nb_output_files = 0;
return main_return_code;
}
So what could be issue? It seems FFmpeg 4.0.2 doesn't release something (resources or its static variables to initial values after the first command)

Adding next lines from FFmpeg 3.2.5 to FFmpeg 4.0.2 to the end of main function solved the problem (I downloaded FFmpeg 3.2.5 as someone's Android project so that user added those lines)
nb_filtergraphs = 0;
nb_input_streams = 0;
nb_input_files = 0;
progress_avio = NULL;
input_streams = NULL;
nb_input_streams = 0;
input_files = NULL;
nb_input_files = 0;
output_streams = NULL;
nb_output_streams = 0;
output_files = NULL;
nb_output_files = 0;

why getpidcon() error on AOSP 7.1.2?

I am working on making a customized bsp based on AOSP Nougat latest source.
Android service process ask service manager to find or add the service.
And service manager try to check mac permissions by calling svc_can_register() or svc_can_find() which calls check_mac_perms() which calls getpidcon().
Let's see svc_can_find()
static int svc_can_find(const uint16_t *name, size_t name_len, pid_t spid, uid_t uid)
{
const char *perm = "find";
return check_mac_perms_from_lookup(spid, uid, perm, str8(name, name_len)) ? 1 : 0;
}
check_mac_perms_from_lookup() is like this:
static bool check_mac_perms_from_lookup(pid_t spid, uid_t uid, const char *perm, const char *name)
{
bool allowed;
char *tctx = NULL;
if (selinux_enabled <= 0) {
return true;
}
if (!sehandle) {
ALOGE("SELinux: Failed to find sehandle. Aborting service_manager.\n");
abort();
}
if (selabel_lookup(sehandle, &tctx, name, 0) != 0) {
ALOGE("SELinux: No match for %s in service_contexts.\n", name);
return false;
}
allowed = check_mac_perms(spid, uid, tctx, perm, name);
freecon(tctx);
return allowed;
}
It calls check_mac_perms(). check_mac_perms() like this:
static bool check_mac_perms(pid_t spid, uid_t uid, const char *tctx, const char *perm, const char *name)
{
char *sctx = NULL;
const char *class = "service_manager";
bool allowed;
struct audit_data ad;
if (getpidcon(spid, &sctx) < 0) {
ALOGE("SELinux: getpidcon(pid=%d) failed to retrieve pid context.\n", spid);
return false;
}
ad.pid = spid;
ad.uid = uid;
ad.name = name;
int result = selinux_check_access(sctx, tctx, class, perm, (void *) &ad);
allowed = (result == 0);
freecon(sctx);
return allowed;
}
It calls getpidcon(). getpidcon() is defined in
external/selinux/libselinux/src/procattr.c
getpidcon() is defined like this:
#define getpidattr_def(fn, attr) \
int get##fn(pid_t pid, char **c) \
{ \
if (pid <= 0) { \
errno = EINVAL; \
return -1; \
} else { \
return getprocattrcon(c, pid, #attr); \
} \
}
...
...
getpidattr_def(pidcon, current)
"getpidattr_def(pidcon, current)" is expanded to getpidcon() function
definition and it calls getprocatrcon()
getprocattrcon() is like this:
static int getprocattrcon(char ** context,
pid_t pid, const char *attr)
{
char *buf;
size_t size;
int fd;
ssize_t ret;
int errno_hold;
fd = openattr(pid, attr, O_RDONLY);
if (fd < 0)
return -1;
size = selinux_page_size;
buf = malloc(size);
if (!buf) {
ret = -1;
goto out;
}
memset(buf, 0, size);
do {
ret = read(fd, buf, size - 1);
} while (ret < 0 && errno == EINTR);
if (ret < 0)
goto out2;
if (ret == 0) {
*context = NULL;
goto out2;
}
*context = strdup(buf);
if (!(*context)) {
ret = -1;
goto out2;
}
ret = 0;
out2:
free(buf);
out:
errno_hold = errno;
close(fd);
errno = errno_hold;
return ret;
}
Pretty simple huh? Just opening some files and reading the contents
and return it by function argument.
It fails at openattr(). I've confirmed this by inserting some log function in
openattr(). openattr() is also simple function.
static int openattr(pid_t pid, const char *attr, int flags)
{
int fd, rc;
char *path;
pid_t tid;
if (pid > 0) {
rc = asprintf(&path, "/proc/%d/attr/%s", pid, attr);
} else if (pid == 0) {
rc = asprintf(&path, "/proc/thread-self/attr/%s", attr);
if (rc < 0)
return -1;
fd = open(path, flags | O_CLOEXEC);
if (fd >= 0 || errno != ENOENT)
goto out;
free(path);
tid = gettid();
rc = asprintf(&path, "/proc/self/task/%d/attr/%s", tid, attr);
} else {
errno = EINVAL;
return -1;
}
if (rc < 0)
return -1;
fd = open(path, flags | O_CLOEXEC);
out:
free(path);
return fd;
}
The fail point is "fd = open(path, flags | O_CLOEXEC);"
Even if the file exists, almost always opening fails. I don't understand ths and want to know what caused the problem. I've confirmed the failure
by inserting some log printing codes, checking android log(adb logcat) and reading the file from android shell(adb shell), e.g. 'cat /proc/412/attr/current'. Reading by 'cat ...' succeeded but log shows the opening the
file fails. The odd thing is if 'pid' is 0, it succeeds.
If opening fails, services can't be launched so the system don't
boot properly. If I ignore the fails and return success from getpidcon()
the system boots properly but this is not the right thing to do obviously.
I'm testing the bsp as selinux permissive mode.
Can anyone have a experience like me? If anyone, please share the
experience and the solution of the problem.
Thank you.
Sangyong Lee.

Recieving text data from remote android bluetooth to Windows xp PC

I want to recieve text data from remote android bluetooth. I had written simple winApi server, but it doesnt respond to remote android sending. The connection was fine and did responds( paired) using control panel manager with my bluetooth. When sending and recieving over control panel manager was working fine. But This time, I want to test using some c++ winapi. Here's my code so far. It was adapted from somewhere codeproject site :)
#include <stdio.h>
#include <stdlib.h>
#include <sstream>
#include <string>
#include <tchar.h>
#include <WinSock2.h>
#include <ws2bth.h>
#include <BluetoothAPIs.h>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
WORD wVersionRequested = 0x202;
WSADATA m_data;
if (0 == WSAStartup(wVersionRequested, &m_data))
{
SOCKET s = socket(AF_BTH, SOCK_STREAM, BTHPROTO_RFCOMM);
const DWORD lastError = GetLastError();
if (s == INVALID_SOCKET)
{
ostringstream stream;
stream << lastError;
string data= stream.str();
printf("Failed to get bluetooth socket! %s\n", data.c_str());
return 1;
}
WSAPROTOCOL_INFO protocolInfo;
int protocolInfoSize = sizeof(protocolInfo);
if (0 != getsockopt(s, SOL_SOCKET, SO_PROTOCOL_INFO,
(char*)&protocolInfo, &protocolInfoSize))
{
return 1;
}
SOCKADDR_BTH address;
address.addressFamily = AF_BTH;
address.btAddr = 0;
address.serviceClassId = GUID_NULL;
address.port = BT_PORT_ANY;
sockaddr *pAddr = (sockaddr*)&address;
if (0 != bind(s, pAddr, sizeof(SOCKADDR_BTH)))
{
ostringstream stream;
stream << GetLastError();
string data= stream.str();
printf("%s\n", data.c_str() );
}
else
{
printf("\nBinding Successful....\n");
int length = sizeof(SOCKADDR_BTH) ;
getsockname(s,(sockaddr*)&address,&length);
wprintf (L"Local Bluetooth device is %04x%08x \nServer channel = %d\n",
GET_NAP(address.btAddr), GET_SAP(address.btAddr), address.port);
}
int size = sizeof(SOCKADDR_BTH);
if (0 != getsockname(s, pAddr, &size))
{
ostringstream stream;
stream << GetLastError();
string data= stream.str();
printf("%s\n", data.c_str());
}
if (0 != listen(s, 10))
{
ostringstream stream;
stream << GetLastError();
string data= stream.str();
printf("%s\n", data.c_str());
}
WSAQUERYSET service;
memset(&service, 0, sizeof(service));
service.dwSize = sizeof(service);
// service.lpszServiceInstanceName = reinterpret_cast<LPWSTR>(_T("Accelerometer Data..."));
//service.lpszServiceInstanceName = ;
// service.lpszComment = reinterpret_cast<LPWSTR>(_T("Pushing data to PC"));
GUID serviceID = OBEXFileTransferServiceClass_UUID;
service.lpServiceClassId = &serviceID;
service.dwNumberOfCsAddrs = 1;
service.dwNameSpace = NS_BTH;
CSADDR_INFO csAddr;
memset(&csAddr, 0, sizeof(csAddr));
csAddr.LocalAddr.iSockaddrLength = sizeof(SOCKADDR_BTH);
csAddr.LocalAddr.lpSockaddr = pAddr;
csAddr.iSocketType = SOCK_STREAM;
csAddr.iProtocol = BTHPROTO_RFCOMM;
service.lpcsaBuffer = &csAddr;
if (0 != WSASetService(&service, RNRSERVICE_REGISTER, 0))
{
printf("Service registration failed....");
ostringstream stream;
stream << GetLastError();
string data= stream.str();
printf("%d\n", data.c_str());
}
else
{
printf("\nService registration Successful....\n");
}
HANDLE hRadio ;
BLUETOOTH_FIND_RADIO_PARAMS btfrp = { sizeof(BLUETOOTH_FIND_RADIO_PARAMS) };
HBLUETOOTH_RADIO_FIND hFind = BluetoothFindFirstRadio(&btfrp, &hRadio);
if ((hFind != NULL)&& (hRadio !=NULL))
{
if (BluetoothEnableDiscovery(hRadio,TRUE)){
printf("BluetoothEnableDiscovery() is working!\n");
}
if (BluetoothEnableIncomingConnections(hRadio,TRUE)){
printf("BluetoothEnableIncomingConnections() is working!\n");
}
if (BluetoothIsConnectable(hRadio)){
printf("BluetoothIsConnectable() is working!\n");
}
}
printf("\nBefore accept.........");
SOCKADDR_BTH sab2;
int ilen = sizeof(sab2);
SOCKET s2 = accept (s,(sockaddr*)&sab2, &ilen);
if (s2 == INVALID_SOCKET)
{
wprintf (L"Socket bind, error %d\n", WSAGetLastError ());
}
wprintf (L"\nConnection came from %04x%08x to channel %d\n",
GET_NAP(sab2.btAddr), GET_SAP(sab2.btAddr), sab2.port);
wprintf (L"\nAfter Accept\n");
char buffer[1024] = {0};
memset(buffer, 0, sizeof(buffer));
int r = recv(s2,(char*)buffer, sizeof(buffer), 0);
printf("%s\n",buffer);
closesocket(s2);
if (0 != WSASetService(&service, RNRSERVICE_DELETE, 0))
{
ostringstream stream;
stream << GetLastError();
string data= stream.str();
printf("%s\n", data.c_str());
}
closesocket(s);
WSACleanup();
return 0;
}
}
I use microsoft BT device btw..

Just to be sure: you said you're on WinXP... OK, but WinXP SP3 with Microsoft BT stack and appropriate dongle? or another XP version and another BT stack (like Widcomm or BlueSoleil...)?
In the later case, BT Socket API won't work...
Otherwise, not much to say about the code, except a missing BluetoothFindRadioClose...

Can't figure out why this code is causing a SIGSEGV when sending packet data

I'm writing some networking code on Android using POSIX sockets but I'm getting a weird SIGSEGV (Signal 11, code 1) when I make a call to sento. I've used the Tombstone trace to determine which line it is, but frankly I can't see what's wrong with it.
References to i_Socket and i_Server have been successful before this particular snippet. I should also mention that the strings are coming from marshaled strings from Mono/Unity.
// Set client informaion
struct addrinfo hints;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC; // We don't care IPv4 or IPv6
hints.ai_socktype = SOCK_DGRAM; // UDP Datagram packets
// Resolve server domain name
int res = getaddrinfo(server, TFTP_PORT, &hints, &i_ServerList);
// Check if we got a valid result
if (res != 0) {
// Report error
if (res == EAI_SYSTEM)
StreamingVideoPluginError("getaddrinfo");
else {
std::stringstream str;
str << "error in getaddrinfo: " << gai_strerror(res);
}
return 1; // No such host
}
// Loop through all entries and bind to the first one we can
bool didBind = false;
for (auto i_Server = i_ServerList; i_Server != nullptr; i_Server = i_Server->ai_next) {
// Try create the socket
if ((i_Socket = socket(i_Server->ai_family, i_Server->ai_socktype, i_Server->ai_protocol)) == -1) {
// Display error
StreamingVideoPluginError("client: socket creation failure");
i_Socket = -1; // Reassert invalid socket
continue;
}
else {
// Binded a socket
didBind = true;
break;
}
}
// Check if we could bind to a server
if (!didBind) {
StreamingVideoPluginError("Failed to bind to a server.");
return 2;
}
// Set socket options
struct timeval tv;
memset(&tv, 0, sizeof (struct timeval));
tv.tv_sec = 5; // 5 second timeout
if (setsockopt(i_Socket, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof tv) == -1)
{
std::stringstream str;
str << "client: could not set timeout. errno =" << errno;
StreamingVideoPluginError(str.str());
return 3;
}
// Make the initial TFTP request
char tftp_buffer[512 + 4];
// Set the opcode to be read request
int packetLength = 0;
tftp_buffer[0] = 0;
tftp_buffer[1] = TFTP_RRQ;
packetLength = 2;
// Place filename
memcpy(&tftp_buffer[packetLength],tftpFileName, strlen(tftpFileName));
packetLength += strlen(tftpFileName);
tftp_buffer[packetLength] = 0; packetLength++;
// Set transfer type to be octet
memcpy(&tftp_buffer[packetLength], TRANSFER_TYPE, strlen(TRANSFER_TYPE));
packetLength += strlen(TRANSFER_TYPE);
tftp_buffer[packetLength] = 0; packetLength++;
std::stringstream str;
str << "Value of packetLength =" << packetLength;
StreamingVideoPluginLog(str.str());
// Send the TFTP request
if (sendto(i_Socket, tftp_buffer, packetLength, 0, i_Server->ai_addr, i_Server->ai_addrlen) == -1) {
// Could not send TFTP request
StreamingVideoPluginError("client: could not send tftp request.");
return 4;
}
Here is the output from NDK-Stack
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 00000018
Stack frame #00 pc 0001e544 /data/app-lib/com.imersia-2/PLUGINNAME.so (ImersiaTftpDa
taSource::Init(char const*, char const*)+1292)
Stack frame #01 pc 0001d428 /data/app-lib/NOPENOPENOPE-2/PLUGINNAME.so (std::priv::_S
TLP_alloc_proxy<char*, char, std::allocator<char> >::~_STLP_alloc_proxy()+16)
addr2line blames
C:/NVPACK/android-ndk-r10/sources/cxx-stl/stlport/stlport/stl/_alloc.h:472

Found out the issue. I was accidentally rebinding i_Server inside the for loop.
for (auto i_Server = i_ServerList; i_Server != nullptr; i_Server = i_Server->ai_next) {
should be
for (i_Server = i_ServerList; i_Server != nullptr; i_Server = i_Server->ai_next) {

CreateProcess for android adb start-server?

When I use CreateProcess to create process adb.exe, It will Block in ReadFile.
void KillAdbProcess()
{
DWORD aProcesses[1024], cbNeeded, cProcesses;
unsigned int i;
if ( !EnumProcesses( aProcesses, sizeof(aProcesses), &cbNeeded ) )
return;
cProcesses = cbNeeded / sizeof(DWORD);
for ( i = 0; i < cProcesses; i++ )
if( aProcesses[i] != 0 ){
bool shouldKill =false;
wchar_t szProcessName[MAX_PATH] = L"<unknown>";
//Get a handle to the process.
HANDLE hProcess = OpenProcess( PROCESS_QUERY_INFORMATION |
PROCESS_VM_READ | PROCESS_TERMINATE,
FALSE, aProcesses[i] );
if (NULL != hProcess )
{
HMODULE hMod;
DWORD cbNeeded;
if ( EnumProcessModules( hProcess, &hMod, sizeof(hMod),
&cbNeeded) )
{
GetModuleFileNameExW( hProcess, hMod, szProcessName,
sizeof(szProcessName)/sizeof(TCHAR));
int len = wcslen(szProcessName);
if(!wcscmp(L"\\adb.exe",szProcessName+len-8)){
shouldKill = true;
}
}
}
if(shouldKill) TerminateProcess(hProcess,0);
CloseHandle( hProcess );
}
}
int testadb(){
KillAdbProcess();
char buff[4096] = {0};
int len = sizeof(buff);
DWORD exitCode = 0;
SECURITY_ATTRIBUTES sa;
ZeroMemory(&sa, sizeof(sa));
sa.bInheritHandle = TRUE;
sa.lpSecurityDescriptor = NULL;
sa.nLength = sizeof(sa);
HANDLE hOutputReadTmp,hOutputRead,hOutputWrite;
// Create the child output pipe.
if (!CreatePipe(&hOutputReadTmp,&hOutputWrite,&sa,0))
return false;
// Create new output read handle and the input write handles. Set
// the Properties to FALSE. Otherwise, the child inherits the
// properties and, as a result, non-closeable handles to the pipes
// are created.
if (!DuplicateHandle(GetCurrentProcess(),hOutputReadTmp,
GetCurrentProcess(),
&hOutputRead, // Address of new handle.
0,FALSE, // Make it uninheritable.
DUPLICATE_SAME_ACCESS))
return false;
// Close inheritable copies of the handles you do not want to be
// inherited.
if (!CloseHandle(hOutputReadTmp)) return false;
PROCESS_INFORMATION pi;
ZeroMemory(&pi, sizeof(pi));
STARTUPINFOW si;
GetStartupInfoW(&si);
si.cb = sizeof(STARTUPINFO);
si.dwFlags = STARTF_USESTDHANDLES;
si.wShowWindow = SW_HIDE;
si.hStdInput = NULL;
if(buff) {
si.hStdOutput = hOutputWrite;
si.hStdError = hOutputWrite;
} else {
si.hStdOutput = NULL;
si.hStdError = NULL;
}
wchar_t cmdBuf[512] = L"adb.exe start-server";
if( !::CreateProcessW(NULL, cmdBuf, NULL, NULL, TRUE, DETACHED_PROCESS, NULL, NULL, &si, &pi) )
{
exitCode = -1;
goto exit;
}
::CloseHandle(hOutputWrite);
hOutputWrite = NULL;
len--; //keep it for string end char.
DWORD dwBytes = 0;
DWORD dwHasRead = 0;
while(::ReadFile(hOutputRead, buff+dwHasRead, len-dwHasRead, &dwBytes, NULL))
{
printf("read byte=%d\n",dwBytes);
if(0 == dwBytes) break;
dwHasRead += dwBytes;
//GetExitCodeProcess(pi.hProcess, &exitCode);
//if(STILL_ACTIVE != exitCode) break;
if(dwHasRead >= len) break;
}
buff[dwHasRead] = 0;
::GetExitCodeProcess(pi.hProcess, &exitCode);
exit:
if(hOutputRead) ::CloseHandle(hOutputRead);
if(hOutputWrite) ::CloseHandle(hOutputWrite);
::CloseHandle(pi.hProcess);
::CloseHandle(pi.hThread);
return 0;
}
If I change code to
while(::ReadFile(hOutputRead, buff+dwHasRead, len-dwHasRead, &dwBytes, NULL))
{
printf("read byte=%d\n",dwBytes);
if(0 == dwBytes) break;
dwHasRead += dwBytes;
GetExitCodeProcess(pi.hProcess, &exitCode);
if(STILL_ACTIVE != exitCode) break;
if(dwHasRead >= len) break;
}
it works, but when I delete printf code, it will block again.
while(::ReadFile(hOutputRead, buff+dwHasRead, len-dwHasRead, &dwBytes, NULL))
{
if(0 == dwBytes) break;
dwHasRead += dwBytes;
GetExitCodeProcess(pi.hProcess, &exitCode);
if(STILL_ACTIVE != exitCode) break;
if(dwHasRead >= len) break;
}
In the code of adb.exe, I see some code like belows:
#if ADB_HOST
int launch_server()
{
#ifdef HAVE_WIN32_PROC
/* we need to start the server in the background */
/* we create a PIPE that will be used to wait for the server's "OK" */
/* message since the pipe handles must be inheritable, we use a */
/* security attribute */
HANDLE pipe_read, pipe_write;
SECURITY_ATTRIBUTES sa;
STARTUPINFO startup;
PROCESS_INFORMATION pinfo;
char program_path[ MAX_PATH ];
int ret;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = TRUE;
/* create pipe, and ensure its read handle isn't inheritable */
ret = CreatePipe( &pipe_read, &pipe_write, &sa, 0 );
if (!ret) {
fprintf(stderr, "CreatePipe() failure, error %ld\n", GetLastError() );
return -1;
}
SetHandleInformation( pipe_read, HANDLE_FLAG_INHERIT, 0 );
ZeroMemory( &startup, sizeof(startup) );
startup.cb = sizeof(startup);
startup.hStdInput = GetStdHandle( STD_INPUT_HANDLE );
startup.hStdOutput = pipe_write;
startup.hStdError = GetStdHandle( STD_ERROR_HANDLE );
startup.dwFlags = STARTF_USESTDHANDLES;
ZeroMemory( &pinfo, sizeof(pinfo) );
/* get path of current program */
GetModuleFileName( NULL, program_path, sizeof(program_path) );
ret = CreateProcess(
program_path, /* program path */
"adb fork-server server",
/* the fork-server argument will set the
debug = 2 in the child */
NULL, /* process handle is not inheritable */
NULL, /* thread handle is not inheritable */
TRUE, /* yes, inherit some handles */
DETACHED_PROCESS, /* the new process doesn't have a console */
NULL, /* use parent's environment block */
NULL, /* use parent's starting directory */
&startup, /* startup info, i.e. std handles */
&pinfo );
CloseHandle( pipe_write );
if (!ret) {
fprintf(stderr, "CreateProcess failure, error %ld\n", GetLastError() );
CloseHandle( pipe_read );
return -1;
}
CloseHandle( pinfo.hProcess );
CloseHandle( pinfo.hThread );
/* wait for the "OK\n" message */
{
char temp[3];
DWORD count;
ret = ReadFile( pipe_read, temp, 3, &count, NULL );
CloseHandle( pipe_read );
if ( !ret ) {
fprintf(stderr, "could not read ok from ADB Server, error = %ld\n", GetLastError() );
return -1;
}
if (count != 3 || temp[0] != 'O' || temp[1] != 'K' || temp[2] != '\n') {
fprintf(stderr, "ADB server didn't ACK\n" );
return -1;
}
}
#elif defined(HAVE_FORKEXEC)
char path[PATH_MAX];
int fd[2];
// set up a pipe so the child can tell us when it is ready.
// fd[0] will be parent's end, and fd[1] will get mapped to stderr in the child.
if (pipe(fd)) {
fprintf(stderr, "pipe failed in launch_server, errno: %d\n", errno);
return -1;
}
get_my_path(path);
pid_t pid = fork();
if(pid < 0) return -1;
if (pid == 0) {
// child side of the fork
// redirect stderr to the pipe
// we use stderr instead of stdout due to stdout's buffering behavior.
adb_close(fd[0]);
dup2(fd[1], STDERR_FILENO);
adb_close(fd[1]);
// child process
int result = execl(path, "adb", "fork-server", "server", NULL);
// this should not return
fprintf(stderr, "OOPS! execl returned %d, errno: %d\n", result, errno);
} else {
// parent side of the fork
char temp[3];
temp[0] = 'A'; temp[1] = 'B'; temp[2] = 'C';
// wait for the "OK\n" message
adb_close(fd[1]);
int ret = adb_read(fd[0], temp, 3);
adb_close(fd[0]);
if (ret < 0) {
fprintf(stderr, "could not read ok from ADB Server, errno = %d\n", errno);
return -1;
}
if (ret != 3 || temp[0] != 'O' || temp[1] != 'K' || temp[2] != '\n') {
fprintf(stderr, "ADB server didn't ACK\n" );
return -1;
}
setsid();
}
#else
#error "cannot implement background server start on this platform"
#endif
return 0;
}
#endif
I think the child process of adb.exe inherit the handle of adb.exe, if the child process of adb.exe doesn't exit, ReadFile will block for ever. But when I exec "adb.exe start-server" in command, all is Ok. So how does windows command call CreateProcess and ReadFile?

I have found the answer: Redirecting an arbitrary Console's Input/Output - CodeProject.
The technique of redirecting the input/output of a console process is very sample: The CreateProcess() API through the STARTUPINFO structure enables us to redirect the standard handles of a child console based process. So we can set these handles to either a pipe handle, file handle, or any handle that we can read and write. The detail of this technique has been described clearly in MSDN: HOWTO: Spawn Console Processes with Redirected Standard Handles.
However, MSDN's sample code has two big problem. First, it assumes the child process will send output at first, then wait for input, then flush the output buffer and exit. If the child process doesn't behave like that, the parent process will be hung up. The reason of this is the ReadFile() function remains blocked untill the child process sends some output, or exits.
Second, It has problem to redirect a 16-bit console (including console based MS-DOS applications.) On Windows 9x, ReadFile remains blocked even after the child process has terminated; On Windows NT/XP, ReadFile always returns FALSE with error code set to ERROR_BROKEN_PIPE if the child process is a DOS application.
Solving the block problem of ReadFile
To prevent the parent process from being blocked by ReadFile, we can simply pass a file handle as stdout to the child process, then monitor this file. A more simple way is to call PeekNamedPipe() function before calling ReadFile(). The PeekNamedPipe function checks information about data in the pipe, then returns immediately. If there's no data available in the pipe, don't call ReadFile.
By calling PeekNamedPipe before ReadFile, we also solve the block problem of redirecting a 16-bit console on Windows 9x.