[ROOT] fgets oddity

From: masik@fzu.cz
Date: Tue Jul 17 2001 - 15:45:20 MEST 

Hi,

has anybody seen a problem reading output of external commands by
fgets after popen (gSystem->OpenPipe) call? It can be noticed as a
garbage/empty line at the end of test/stress output where system info
is being obtained. I've seen this on Debian/PPC and some Debian/x86
(but not all machines fail). As for non-linux boxes I had a chance to
test only dxplus(OSF1) at CERN for which it is less frequent but it
happens too. Root version is 3.01/06, libc-2.2.3-6, Linux version
2.4.6-pre8, gcc-3.0.

Please see the following example
[dxplus02] /afs/cern.ch/user/j/jmasik/public > g++ -I$ROOTSYS/include poproot2.cxx `root-config --libs` [dxplus02] /afs/cern.ch/user/j/jmasik/public > ./a.out fgets returned NULL [dxplus02] /afs/cern.ch/user/j/jmasik/public > ./a.out * OSF1 dxplus02 V4.0 1229 alpha Any information on popen and fgets I have doesn't mention the need to test anything beyond returned pointers. Bad runs have this line in their tracelogs. read(4, 0x30018000, 4096) = ? ERESTARTSYS (To be restarted) Do you have an idea what's wrong? Everything works if I comment out TSystem.h and remove `root-config --libs` from the compile command on Debian/PPC, on OSF removing TSystem.h is enough. Jiri I don't know how to strace on OSF, on Linux it looks like .... open("/data/masik/root-v3.02.gcc3/include/RQ_OBJECT.h", O_RDONLY) = 3 brk(0x103ae000) = 0x103ae000 fstat64(0x3, 0x7fffe938) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x30017000 read(3, "// @(#)root/base:$Name: $:$Id: "..., 4096) = 4096 _llseek(0x3, 0, 0, 0x7fffe8f8, 0) = 0 read(3, "// @(#)root/base:$Name: $:$Id: "..., 4096) = 4096 read(3, "ar *method) \\\n { Emit(\"Chan"..., 4096) = 152 read(3, "", 4096) = 0 pipe([4, 5]) = 0 fork() = 4880 close(5) = 0 fstat64(0x4, 0x7ffff0c8) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x30018000 read(4, 0x30018000, 4096) = ? ERESTARTSYS (To be restarted) --- SIGCHLD (Child exited) --- fstat64(0x1, 0x7fffe9e8) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x30019000 ioctl(1, 0x402c7413, 0x7fffe848) = 0 write(1, "fgets returned NULL\n", 20) = 20

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