[lld] r343698 - lld-link: Several tweaks to default entry point selection.
Nico Weber via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 3 10:01:40 PDT 2018
Author: nico
Date: Wed Oct 3 10:01:39 2018
New Revision: 343698
URL: http://llvm.org/viewvc/llvm-project?rev=343698&view=rev
Log:
lld-link: Several tweaks to default entry point selection.
Three related changes:
1. link.exe uses the presence of main and wmain to decide if it should call
mainCRTStartup or wmainCRTStartup, even if /nodefaultlib is passed. For
compatibility, remove FindMain logic.
2. Default to the non-wide entrypoint if main is not found. This has two effects:
2a. In normal links, lld-link now prints
lld-link: error: undefined symbol: _main
>>> referenced by f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:78
>>> libcmt.lib(exe_main.obj):("int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ))
>>> referenced by f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:283
>>> libcmt.lib(exe_main.obj):("int __cdecl __scrt_common_main_seh(void)" (?__scrt_common_main_seh@@YAHXZ))
instead of
lld-link: error: entry point must be defined
This is arguably a better error message, since it now mentions that _main is
missing. (This matches link.exe's diagnostic in this case.)
2b. With /nodefautlib, we now default to mainCRTStartup if no main() is
present, again matching link.exe. This makes r337407 obsolete.
This means if you have a cc file containing both mainCRTStartup and
wmainCRTStartup and you pass /nodefaultlib /subsystem:console, lld-link will
now call mainCRTStartup, matching link.exe
3. Print a warning if both main and wmain are present, similar to link.exe's
LNK4067.
Differential Revision: https://reviews.llvm.org/D52832
Modified:
lld/trunk/COFF/Driver.cpp
lld/trunk/test/COFF/entry-inference.test
lld/trunk/test/COFF/entry-inference4.test
Modified: lld/trunk/COFF/Driver.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Driver.cpp?rev=343698&r1=343697&r2=343698&view=diff
==============================================================================
--- lld/trunk/COFF/Driver.cpp (original)
+++ lld/trunk/COFF/Driver.cpp Wed Oct 3 10:01:39 2018
@@ -430,26 +430,28 @@ StringRef LinkerDriver::findDefaultEntry
assert(Config->Subsystem != IMAGE_SUBSYSTEM_UNKNOWN &&
"must handle /subsystem before calling this");
- // As a special case, if /nodefaultlib is given, we directly look for an
- // entry point. This is because, if no default library is linked, users
- // need to define an entry point instead of a "main".
- bool FindMain = !Config->NoDefaultLibAll;
if (Config->Subsystem == IMAGE_SUBSYSTEM_WINDOWS_GUI) {
- if (findUnderscoreMangle(FindMain ? "WinMain" : "WinMainCRTStartup"))
- return mangle("WinMainCRTStartup");
- if (findUnderscoreMangle(FindMain ? "wWinMain" : "wWinMainCRTStartup"))
- return mangle("wWinMainCRTStartup");
+ if (findUnderscoreMangle("wWinMain")) {
+ if (!findUnderscoreMangle("WinMain"))
+ return mangle("wWinMainCRTStartup");
+ warn("found both wWinMain and WinMain; using latter");
+ }
+ return mangle("WinMainCRTStartup");
}
- if (findUnderscoreMangle(FindMain ? "main" : "mainCRTStartup"))
- return mangle("mainCRTStartup");
- if (findUnderscoreMangle(FindMain ? "wmain" : "wmainCRTStartup"))
- return mangle("wmainCRTStartup");
- return "";
+ if (findUnderscoreMangle("wmain")) {
+ if (!findUnderscoreMangle("main"))
+ return mangle("wmainCRTStartup");
+ warn("found both wmain and main; using latter");
+ }
+ return mangle("mainCRTStartup");
}
WindowsSubsystem LinkerDriver::inferSubsystem() {
if (Config->DLL)
return IMAGE_SUBSYSTEM_WINDOWS_GUI;
+ // Note that link.exe infers the subsystem from the presence of these
+ // functions even if /entry: or /nodefaultlib are passed which causes them
+ // to not be called.
bool HaveMain = findUnderscoreMangle("main");
bool HaveWMain = findUnderscoreMangle("wmain");
bool HaveWinMain = findUnderscoreMangle("WinMain");
Modified: lld/trunk/test/COFF/entry-inference.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/entry-inference.test?rev=343698&r1=343697&r2=343698&view=diff
==============================================================================
--- lld/trunk/test/COFF/entry-inference.test (original)
+++ lld/trunk/test/COFF/entry-inference.test Wed Oct 3 10:01:39 2018
@@ -1,18 +1,26 @@
# RUN: sed -e s/ENTRYNAME/main/ %s | yaml2obj > %t.obj
# RUN: not lld-link /out:%t.exe %t.obj > %t.log 2>&1
# RUN: FileCheck -check-prefix=MAIN %s < %t.log
+# RUN: not lld-link /nodefaultlib /out:%t.exe %t.obj > %t.log 2>&1
+# RUN: FileCheck -check-prefix=MAIN %s < %t.log
# RUN: sed s/ENTRYNAME/wmain/ %s | yaml2obj > %t.obj
# RUN: not lld-link /out:%t.exe %t.obj > %t.log 2>&1
# RUN: FileCheck -check-prefix=WMAIN %s < %t.log
+# RUN: not lld-link /nodefaultlib /out:%t.exe %t.obj > %t.log 2>&1
+# RUN: FileCheck -check-prefix=WMAIN %s < %t.log
# RUN: sed s/ENTRYNAME/WinMain/ %s | yaml2obj > %t.obj
# RUN: not lld-link /out:%t.exe %t.obj > %t.log 2>&1
# RUN: FileCheck -check-prefix=WINMAIN %s < %t.log
+# RUN: not lld-link /nodefaultlib /out:%t.exe %t.obj > %t.log 2>&1
+# RUN: FileCheck -check-prefix=WINMAIN %s < %t.log
# RUN: sed s/ENTRYNAME/wWinMain/ %s | yaml2obj > %t.obj
# RUN: not lld-link /out:%t.exe %t.obj > %t.log 2>&1
# RUN: FileCheck -check-prefix=WWINMAIN %s < %t.log
+# RUN: not lld-link /nodefaultlib /out:%t.exe %t.obj > %t.log 2>&1
+# RUN: FileCheck -check-prefix=WWINMAIN %s < %t.log
# MAIN: error: <root>: undefined symbol: mainCRTStartup
# WMAIN: error: <root>: undefined symbol: wmainCRTStartup
Modified: lld/trunk/test/COFF/entry-inference4.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/entry-inference4.test?rev=343698&r1=343697&r2=343698&view=diff
==============================================================================
--- lld/trunk/test/COFF/entry-inference4.test (original)
+++ lld/trunk/test/COFF/entry-inference4.test Wed Oct 3 10:01:39 2018
@@ -14,10 +14,22 @@
# RUN: not lld-link /subsystem:console /out:%t.exe %t.obj > %t.log 2>&1
# RUN: FileCheck -check-prefix=WMAIN %s < %t.log
-# MAIN: error: <root>: undefined symbol: mainCRTStartup
-# WMAIN: error: <root>: undefined symbol: wmainCRTStartup
-# WINMAIN: error: <root>: undefined symbol: WinMainCRTStartup
-# WWINMAIN: error: <root>: undefined symbol: wWinMainCRTStartup
+# RUN: sed 's/ENTRY1/wmain/;s/ENTRY2/main/' %s | yaml2obj > %t.obj
+# RUN: not lld-link /out:%t.exe %t.obj > %t.log 2>&1
+# RUN: FileCheck -check-prefix=MAINWMAIN %s < %t.log
+
+# RUN: sed 's/ENTRY1/wWinMain/;s/ENTRY2/WinMain/' %s | yaml2obj > %t.obj
+# RUN: not lld-link /out:%t.exe %t.obj > %t.log 2>&1
+# RUN: FileCheck -check-prefix=WINMAINWWINMAIN %s < %t.log
+
+# MAIN: error: <root>: undefined symbol: mainCRTStartup
+# WMAIN: error: <root>: undefined symbol: wmainCRTStartup
+# MAINWMAIN: warning: found both wmain and main; using latter
+# MAINWMAIN: error: <root>: undefined symbol: mainCRTStartup
+# WINMAIN: error: <root>: undefined symbol: WinMainCRTStartup
+# WWINMAIN: error: <root>: undefined symbol: wWinMainCRTStartup
+# WINMAINWWINMAIN: warning: found both wWinMain and WinMain; using latter
+# WINMAINWWINMAIN: error: <root>: undefined symbol: WinMainCRTStartup
--- !COFF
header:
More information about the llvm-commits
mailing list