On Tue, 20 Oct 2015, Martin Storsjo wrote:
Since MSVC 2015/Windows 10, the C runtime has now been split into two parts, ucrtbase, which is the generic C runtime which is now considered a system component, and vcruntimeX which is specific to the compiler version.
This DLL is built using only a small subset of the msvcrt source files. In particular, the DLL should not use most of the global CRT state as a normal msvcrt carries - the only TLS state handled is for exceptions.
The functions in main.c are simplified versions of the corresponding ones from msvcrt. Additionally, two stub functions (relating to telemetry) are added; they are required for a plain empty exe built with MSVC 2015 with dynamic C runtime to start up with the builtin vcruntime140.dll.
Some functions that are available in the full msvcrt, that vcruntime140.dll should export, are not included since they haven't been split off to be buildable without the full internals of msvcrt yet. Those functions are: _CxxThrowException __AdjustPointer __RTCastToVoid __RTDynamicCast __RTtypeid _chkesp _get_unexpected
Signed-off-by: Martin Storsjo martin@martin.st
Changed since last version: Moved main-vcruntime.c to the vcruntime140 directory; skipped the separate memory.c and included all of it in the vcruntime main.c instead. Removed a leftover commented out statement.
In this build configuration, some functions use simpler error handling
- instead of calling _amsg_exit, it calls ExitProcess directly.
(_amsg_exit checks the error mode, which is state that lives within ucrtbase.dll; vcruntime140.dll shouldn't have a separate copy of that state, and there's no function in ucrtbase.dll that would allow quering it.)
configure.ac | 1 + dlls/msvcrt/except.c | 4 + dlls/msvcrt/except_i386.c | 4 + dlls/vcruntime140/Makefile.in | 12 ++ dlls/vcruntime140/main.c | 224 ++++++++++++++++++++++++++++++++++++ dlls/vcruntime140/vcruntime140.spec | 87 ++++++++++++++ 6 files changed, 332 insertions(+) create mode 100644 dlls/vcruntime140/Makefile.in create mode 100644 dlls/vcruntime140/main.c create mode 100644 dlls/vcruntime140/vcruntime140.spec
Piotr asked whether this would make sense as a DLL that only forwards calls down to ucrtbase, instead of a standalone DLL that duplicates the implementation.
For i386, this DLL has got 81 exported functions, and all of those except a few do exist in ucrtbase.dll. The ones that are unique to vcruntime140.dll are the following:
__C_specific_handler_noexcept __std_terminate __telemetry_main_invoke_trigger __telemetry_main_return_trigger __uncaught_exceptions __vcrt_GetModuleFileNameW __vcrt_GetModuleHandleW __vcrt_InitializeCriticalSectionEx __vcrt_LoadLibraryExW
Out of these, the telemetry ones actually are called implicitly even in a plain hello world executable built with MSVC 2015 (but having them as empty stubs seems to work fine so far), the other ones I haven't had reason to look into yet.
The real vcruntime140.dll actually also do some calls to ucrtbase.dll (linked via the api-ms-win-crt-* stub dlls), but not all the real functions - it only links to the following ones: terminate abort strcpy_s malloc _free_base free _malloc_base _calloc_base __stdio_common_vsprintf_s atol
(Additionally it links to a few symbols from kernel32.dll and one from advapi32.dll.)
Given this, I still think this DLL makes sense as a standalone DLL instead of just a stub forwarding to ucrtbase, since that's what the original one does as well. At worst some of the functions may need to have subtly different behaviour in different versions (which I guess is the main reason for the DLL existing in the first place).
// Martin
Martin Storsjö martin@martin.st writes:
The real vcruntime140.dll actually also do some calls to ucrtbase.dll (linked via the api-ms-win-crt-* stub dlls), but not all the real functions - it only links to the following ones: terminate abort strcpy_s malloc _free_base free _malloc_base _calloc_base __stdio_common_vsprintf_s atol
(Additionally it links to a few symbols from kernel32.dll and one from advapi32.dll.)
Please don't look into the internal details of the native dll.
Given this, I still think this DLL makes sense as a standalone DLL instead of just a stub forwarding to ucrtbase, since that's what the original one does as well. At worst some of the functions may need to have subtly different behaviour in different versions (which I guess is the main reason for the DLL existing in the first place).
It seems to me that you should start with a forwarding stub. If at some point there's a good reason for duplicating things, we can do it then.
On Wed, 28 Oct 2015, Alexandre Julliard wrote:
Martin Storsjö martin@martin.st writes:
The real vcruntime140.dll actually also do some calls to ucrtbase.dll (linked via the api-ms-win-crt-* stub dlls), but not all the real functions - it only links to the following ones: terminate abort strcpy_s malloc _free_base free _malloc_base _calloc_base __stdio_common_vsprintf_s atol
(Additionally it links to a few symbols from kernel32.dll and one from advapi32.dll.)
Please don't look into the internal details of the native dll.
Given this, I still think this DLL makes sense as a standalone DLL instead of just a stub forwarding to ucrtbase, since that's what the original one does as well. At worst some of the functions may need to have subtly different behaviour in different versions (which I guess is the main reason for the DLL existing in the first place).
It seems to me that you should start with a forwarding stub. If at some point there's a good reason for duplicating things, we can do it then.
Ok, that makes sense. In this case, I think all of it can be forwarded, except for the telemetry function stubs.
// Martin
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Alexandre Julliard -
Martin Storsjö