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[llvm-lib] Add /WX, warn by default on empty inputs, add opt-out

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lib.exe by default exits successfully without writing an output
file when no inputs are passed. llvm-lib has the same behavior,
for compatibility.

This behavior interacts poorly with build systems: If a static
library target had no inputs, llvm-lib would not produce an output
file, causing ninja (or make, or a similar system) to successfully
run that step, but then re-run it on the next build.

After this patch, llvm-lib emits a warning in this case, that with
/WX can be turned into an error. That way, ninja (or make, or...)
will mark the initial build as failed.

People who don't like the warning can use /ignore:emptyoutput to
suppress it.

The warning also points out the existing flag /llvmlibempty which
forces creation of an empty .lib file (this is an extension to lib.exe).

Differential Revision: https://reviews.llvm.org/D123517
This commit is contained in:
Nico Weber 2022-04-11 11:01:34 -04:00
parent 76192182d0
commit 75196b99fb
4 changed files with 51 additions and 11 deletions
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3
lld/COFF/Options.td
View File

@ -166,7 +166,8 @@ def force_multiple : F<"force:multiple">,
HelpText<"Allow multiply defined symbols when creating executables">;
def force_multipleres : F<"force:multipleres">,
HelpText<"Allow multiply defined resources when creating executables">;
defm WX : B<"WX", "Treat warnings as errors", "Don't treat warnings as errors">;
defm WX : B<"WX", "Treat warnings as errors",
"Don't treat warnings as errors (default)">;
defm allowbind : B<"allowbind", "Enable DLL binding (default)",
"Disable DLL binding">;

26
llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
View File

@ -229,10 +229,11 @@ static void appendFile(std::vector<NewArchiveMember> &Members,
(Magic == file_magic::coff_object) ? getCOFFFileMachine(MB)
: getBitcodeFileMachine(MB);
if (!MaybeFileMachine) {
handleAllErrors(MaybeFileMachine.takeError(), [&](const ErrorInfoBase &EIB) {
llvm::errs() << MB.getBufferIdentifier() << ": " << EIB.message()
<< "\n";
});
handleAllErrors(MaybeFileMachine.takeError(),
[&](const ErrorInfoBase &EIB) {
llvm::errs() << MB.getBufferIdentifier() << ": "
<< EIB.message() << "\n";
});
exit(1);
}
COFF::MachineTypes FileMachine = *MaybeFileMachine;
@ -291,10 +292,25 @@ int llvm::libDriverMain(ArrayRef<const char *> ArgsArr) {
return 0;
}
// Parse /ignore:
llvm::StringSet<> IgnoredWarnings;
for (auto *Arg : Args.filtered(OPT_ignore))
IgnoredWarnings.insert(Arg->getValue());
// If no input files and not told otherwise, silently do nothing to match
// lib.exe
if (!Args.hasArgNoClaim(OPT_INPUT) && !Args.hasArg(OPT_llvmlibempty))
if (!Args.hasArgNoClaim(OPT_INPUT) && !Args.hasArg(OPT_llvmlibempty)) {
if (!IgnoredWarnings.contains("emptyoutput")) {
llvm::errs() << "warning: no input files, not writing output file\n";
llvm::errs() << " pass /llvmlibempty to write empty .lib file,\n";
llvm::errs() << " pass /ignore:emptyoutput to suppress warning\n";
if (Args.hasFlag(OPT_WX, OPT_WX_no, false)) {
llvm::errs() << "treating warning as error due to /WX\n";
return 1;
}
}
return 0;
}
if (Args.hasArg(OPT_lst)) {
doList(Args);

14
llvm/lib/ToolDrivers/llvm-lib/Options.td
View File

@ -9,6 +9,14 @@ class F<string name> : Flag<["/", "-", "/?", "-?"], name>;
class P<string name, string help> :
Joined<["/", "-", "/?", "-?"], name#":">, HelpText<help>;
// Boolean flag which can be suffixed by ":no". Using it unsuffixed turns the
// flag on and using it suffixed by ":no" turns it off.
multiclass B<string name, string help_on, string help_off> {
def "" : F<name>, HelpText<help_on>;
def _no : F<name#":no">, HelpText<help_off>;
}
def ignore : P<"ignore", "Specify warning codes to ignore">;
def libpath: P<"libpath", "Object file search path">;
// Can't be called "list" since that's a keyword.
@ -23,6 +31,9 @@ def llvmlibempty : F<"llvmlibempty">,
def machine: P<"machine", "Specify target platform">;
defm WX : B<"WX", "Treat warnings as errors",
"Don't treat warnings as errors (default)">;
def help : F<"help">;
// /?? and -?? must be before /? and -? to not confuse lib/Options.
@ -32,7 +43,4 @@ def help_q : Flag<["/??", "-??", "/?", "-?"], "">, Alias<help>;
// The flags below do nothing. They are defined only for lib.exe compatibility.
//==============================================================================
class QF<string name> : Joined<["/", "-", "/?", "-?"], name#":">;
def ignore : QF<"ignore">;
def nologo : F<"nologo">;

19
llvm/test/tools/llvm-lib/no-inputs.test
View File

@ -1,7 +1,22 @@
RUN: rm -f %t.lib
RUN: llvm-lib -out:%t.lib
RUN: llvm-lib -out:%t.lib 2>&1 | FileCheck --check-prefix=EMPTYWARN %s
RUN: test ! -e %t.lib
RUN: not llvm-lib -out:%t.lib /WX 2>&1 | FileCheck --check-prefix=EMPTYWARN %s
RUN: test ! -e %t.lib
RUN: llvm-lib -out:%t.lib /WX /WX:no 2>&1 \
RUN: | FileCheck --check-prefix=EMPTYWARN %s
RUN: test ! -e %t.lib
RUN: llvm-lib /ignore:emptyoutput -out:%t.lib 2>&1 \
RUN: | FileCheck --check-prefix=NOEMPTYWARN --allow-empty %s
RUN: test ! -e %t.lib
RUN: llvm-lib /ignore:emptyoutput /WX -out:%t.lib 2>&1 \
RUN: | FileCheck --check-prefix=NOEMPTYWARN --allow-empty %s
RUN: test ! -e %t.lib
RUN: llvm-lib /llvmlibempty -out:%t.lib
EMPTYWARN: warning: no input files, not writing output file
NOEMPTYWARN-NOT: warning: no input files, not writing output file
RUN: llvm-lib /llvmlibempty -out:%t.lib 2>&1 \
RUN: | FileCheck --check-prefix=NOEMPTYWARN --allow-empty %s
RUN: FileCheck %s < %t.lib
CHECK: !<arch>