Registry writes only 4 Chars

Question

When im try to write a RegEdit Key, he only writes only the first 4 Charaters of the file path.

HKEY hKey;
RegOpenKeyEx(HKEY_CURRENT_USER, "Software\\Microsoft\\Windows\\CurrentVersion\\Run", 0, KEY_SET_VALUE, &hKey);
RegSetValueEx(hKey, "Test", 0, REG_SZ, (BYTE*)file, sizeof(file));
RegCloseKey(hKey);

I can't reproduce this code because `file` is not defined. – Drew Dormann Jul 15 '15 at 22:51 — Drew Dormann, Jul 15 '15 at 22:51

score 2 · Answer 1 · edited Jul 16 '15 at 15:14

2

sizeof(pointer) gives 4 on 32 bit systems. Try string::size (online documentation) instead.

std::string filename ("file.exe");
RegSetValueEx( ..., filename.size());

edited Jul 16 '15 at 15:14

IInspectable

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answered Jul 15 '15 at 22:51

Thomas Weller

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score 1 · Accepted Answer · answered Jul 15 '15 at 22:50

1

Apparently your file is a pointer. sizeof(file) is size of pointer in bytes, which is 4 on your platform.

What is file? How is it declared? What does it point to? Why are you using sizeof on it in order to determine how many bytes to write? If file is a pointer to a C-style string, then sizeof will not help you to determine the length of that string. You need strlen for that.

answered Jul 15 '15 at 22:50

AnT stands with Russia

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file is a char array – zemicolon Jul 15 '15 at 22:55
@noaaah an *array* or a *pointer to an array*? – Drew Dormann Jul 15 '15 at 22:59
@noaaah: Unlikely. Apparently `file` is a `char *` pointer. – AnT stands with Russia Jul 15 '15 at 23:51

score 1 · Answer 3 · answered Jul 15 '15 at 23:02

If file is a char array, then...

RegSetValueEx(hKey, "Test", 0, REG_SZ, (BYTE*)file, strlen(file) + 1); // API says to include terminating NULL.

"The size of the information pointed to by the lpData parameter, in bytes. If the data is of type REG_SZ, REG_EXPAND_SZ, or REG_MULTI_SZ, cbData must include the size of the terminating null character or characters."

https://msdn.microsoft.com/en-us/library/windows/desktop/ms724923(v=vs.85).aspx

Registry writes only 4 Chars

3 Answers3