Windows Mobile FAQ

Windows Mobile FAQ
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What if my Windows Mobile device does not support SetFilePointer and/or SetEndOfFile?
You can manually disable the truncate functionality from the build.
Do that by opening the db-X.X.X/build_wince/db_config.h file, and change the line that reads
```
#define HAVE_FTRUCATE 1
```
to read
```
#undef HAVE_FTRUNCATE
```
Making this change disables DB->compact() for btree databases.
Why doesn't automatic log archiving work?
The Windows Mobile platform does not have a concept of a working directory. This means that the DB_ARCH_REMOVE and DB_ARCH_ABS flags do not work properly within Windows Mobile, because they rely on having a working directory.

To work around this issue, you can call log_archive with the DB_ARCH_LOG flag, the list of returned file handles will not contain absolute paths. Your application can take this list of files, construct absolute paths, and delete the files.
Does Berkeley DB support Windows Mobile?
Yes.

Berkeley DB relies on a subset of the Windows API, and some standard C library APIs. These are provided by Windows CE. Windows Mobile is built "on top" of Windows CE.
Does Berkeley DB support Windows CE?
Yes.

Berkeley DB relies on a subset of the Windows API, and some standard C library APIs. These are provided by Windows CE.
Does Berkeley DB support Windows Embedded Compact 7?
Yes.

Starting from release 12.1.6.1, it is possible to build Berkeley DB on Windows Embedded Compact 7. Below are tips for the build process:
1. Compile error at line 146 in stdlib.h
  This is a known bug for the Windows Embedded Compact 7 SDK. A workaround is to change the line 146 in stdlib.h to read:
```
__checkReturn __bcount(_Size) void * __cdecl _alloca(__in size_t 
_Size);
```
2. error LNK2019: unresolved external symbol _localtime_s referenced in function _osLocaltime
  This link error is caused by the fact that the Windows Embedded Compact 7 runtime used to link Berkeley DB does not provide the localtime_s() function. A workaround is to add
```
HAVE_LOCALTIME_S=0
```
  to the proprocessor definitions of the db_sql project. This can be done by right clicking the db_sql project, select Properties->Configuration Properties->C/C++->Preprocessor->Proprocessor Definitions, and append
```
HAVE_LOCALTIME_S=0
```
  at the end of the list.
3. error LNK1221: a subsystem can't be inferred and must be defined
  This link error happens on Visual Studio 2008, because it cannot understand the subsystem configured for Visual Studio 2005. To fix this error, right click the project reporting this link error, select Properties->Configuration Properties-> Linker->System->SubSystem, and change the value to WindowsCE (/SUBSYSTEM:WINDOWSCE).
4. warning C4996: 'xxx': This function or variable may be unsafe.
  Used within the Berkeley DB source tree, these functions are actually safe. You can safely ignore these warnings.
What platforms are the supplied sample applications designed for?
The supplied sample applications were developed for the Pocket PC 2003 emulator. They are known to work on real pocket PC devices and later versions of the emulator as well.

The supplied applications are not designed to work with Smartphone devices. The screen size and input mechanisms are not compatible.
I see a file mapping error when opening a Berkeley DB environment or database. What is wrong?
The default behavior of Berkeley DB is to use memory mapped files in the environment. Windows Mobile does not allow memory mapped files to be created on flash storage.

There are two workarounds:
1. Configure the Berkeley DB environment not to use memory mapped files. The options are discussed in detail in Shared memory region.
2. Create the Berkeley DB environment on non-flash storage. It is possible to store database and log files in a different location to using the DB_ENV->add_data_dir() and DB_ENV->set_lg_dir() APIs.

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