New subject: [Bug 37940] Invalid file buffering behavior causes data corruption

21 Jan 2015


      https://bugs.winehq.org/show_bug.cgi?id=37940
Bug ID: 37940
           Summary: Invalid file buffering behavior causes data corruption
           Product: Wine
           Version: 1.7.34
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: major
          Priority: P2
         Component: msvcrt
          Assignee: wine-bugs@winehq.org
          Reporter: ho-rr-or@mail.ru
      Distribution: ---
Created attachment 50543
  --> https://bugs.winehq.org/attachment.cgi?id=50543
Compiled binary to reproduce
msvcrt file routines sometimes corrupt file data by invalid buffer flushing.
Reproduced by following code (compiled binary attached):
char data[68200];
    char buf[sizeof(data)];
    for (int i = 0; i < sizeof(data); i++)
        data[i] = rand();
FILE* f = _wfsopen(L"test.bin", L"wb+", 64);
rewind(f);
    fwrite(data, 1, 68100, f);
// Following calls possible corrupt buffer
    rewind(f);
    fread(buf, 1, 40000, f);
    fread(buf, 1, 40000, f);
// Following call causes wrong buffer flushing
    fwrite(&data[68100], 1, 100, f);
fclose(f);
f = fopen("test.bin", "rb");
    fread(buf, 1, sizeof(buf), f);
    fclose(f);
    printf("Memcmp: %d\n", memcmp(data, buf, sizeof(buf)));
Windows output:
Memcmp: 0
Wine output:
Memcmp: -1
Windows file size: 68200
Wine file size: 72296
Bug causes at least cl.exe in Microsoft Visual Studio 2008/2010. Reproduced
when cl.exe generates precompiled header.
test.h:
#pragma once
#include "Windows.h"
#include <iostream>
test.cpp:
#include "test.h"
int main()
{
   std::cout << "WORKS!" << std::endl;
   return 0;
}
Command to reproduce:
rm test.pch; wine cl.exe /Yctest.h test.cpp
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[Bug 37940] New: Invalid file buffering behavior causes data corruption