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[5.7][Autolink Extract] Keep a set of seen linker library flags #59034

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[5.7][Autolink Extract] Keep a set of seen linker library flags #59034

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36 changes: 28 additions & 8 deletions lib/DriverTool/autolink_extract_main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@

#include <string>
#include <vector>
#include <unordered_set>

#include "swift/AST/DiagnosticsFrontend.h"
#include "swift/Frontend/Frontend.h"
Expand Down Expand Up @@ -112,6 +113,7 @@ class AutolinkExtractInvocation {
/// Return 'true' if there was an error, and 'false' otherwise.
static bool
extractLinkerFlagsFromObjectFile(const llvm::object::ObjectFile *ObjectFile,
std::unordered_set<std::string> &SeenLinkerLibraryFlags,
std::vector<std::string> &LinkerFlags,
CompilerInstance &Instance) {
// Search for the section we hold autolink entries in
Expand Down Expand Up @@ -140,8 +142,15 @@ extractLinkerFlagsFromObjectFile(const llvm::object::ObjectFile *ObjectFile,
llvm::SmallVector<llvm::StringRef, 4> SplitFlags;
SectionData->split(SplitFlags, llvm::StringRef("\0", 1), -1,
/*KeepEmpty=*/false);
for (const auto &Flag : SplitFlags)
LinkerFlags.push_back(Flag.str());
for (const auto &Flag : SplitFlags) {
// If this is a library '-lxxx' flag, only add it if we have not seen it before
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I worry about this approach because you have to consider the following equivalences:

  1. -l:library.a
  2. -static -lrary
  3. lib/library.a

and the following:

  1. -l:library.so
  2. -shared -lrary
  3. lib/liblibrary.so

Furthermore, the order of the libraries is relevant to linking. The conversion to an unordered_set breaks linking semantics - order of library specification on the command line indicates how to resolve symbols. This can change the symbolic resolution.

if (Flag.str().rfind("-l", 0) == 0) {
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Why std::string::rfind over std::string::compare which would be more idiomatic and clearer?

auto SeenFlagsInsertResult = SeenLinkerLibraryFlags.insert(Flag.str());
if (SeenFlagsInsertResult.second == true)
LinkerFlags.push_back(Flag.str());
} else
LinkerFlags.push_back(Flag.str());
}
}
}
return false;
Expand All @@ -152,6 +161,7 @@ extractLinkerFlagsFromObjectFile(const llvm::object::ObjectFile *ObjectFile,
/// 'true' if there was an error, and 'false' otherwise.
static bool
extractLinkerFlagsFromObjectFile(const llvm::object::WasmObjectFile *ObjectFile,
std::unordered_set<std::string> &SeenLinkerLibraryFlags,
std::vector<std::string> &LinkerFlags,
CompilerInstance &Instance) {
// Search for the data segment we hold autolink entries in
Expand All @@ -164,8 +174,15 @@ extractLinkerFlagsFromObjectFile(const llvm::object::WasmObjectFile *ObjectFile,
llvm::SmallVector<llvm::StringRef, 4> SplitFlags;
SegmentData.split(SplitFlags, llvm::StringRef("\0", 1), -1,
/*KeepEmpty=*/false);
for (const auto &Flag : SplitFlags)
LinkerFlags.push_back(Flag.str());
for (const auto &Flag : SplitFlags) {
// If this is a library '-lxxx' flag, only add it if we have not seen it before
if (Flag.str().rfind("-l", 0) == 0) {
auto SeenFlagsInsertResult = SeenLinkerLibraryFlags.insert(Flag.str());
if (SeenFlagsInsertResult.second == true)
LinkerFlags.push_back(Flag.str());
} else
LinkerFlags.push_back(Flag.str());
}
}
}
return false;
Expand All @@ -178,12 +195,13 @@ extractLinkerFlagsFromObjectFile(const llvm::object::WasmObjectFile *ObjectFile,
static bool extractLinkerFlags(const llvm::object::Binary *Bin,
CompilerInstance &Instance,
StringRef BinaryFileName,
std::unordered_set<std::string> &SeenLinkerLibraryFlags,
std::vector<std::string> &LinkerFlags) {
if (auto *ObjectFile = llvm::dyn_cast<llvm::object::ELFObjectFileBase>(Bin)) {
return extractLinkerFlagsFromObjectFile(ObjectFile, LinkerFlags, Instance);
return extractLinkerFlagsFromObjectFile(ObjectFile, SeenLinkerLibraryFlags, LinkerFlags, Instance);
} else if (auto *ObjectFile =
llvm::dyn_cast<llvm::object::WasmObjectFile>(Bin)) {
return extractLinkerFlagsFromObjectFile(ObjectFile, LinkerFlags, Instance);
return extractLinkerFlagsFromObjectFile(ObjectFile, SeenLinkerLibraryFlags, LinkerFlags, Instance);
} else if (auto *Archive = llvm::dyn_cast<llvm::object::Archive>(Bin)) {
llvm::Error Error = llvm::Error::success();
for (const auto &Child : Archive->children(Error)) {
Expand All @@ -197,7 +215,7 @@ static bool extractLinkerFlags(const llvm::object::Binary *Bin,
return true;
}
if (extractLinkerFlags(ChildBinary->get(), Instance, BinaryFileName,
LinkerFlags)) {
SeenLinkerLibraryFlags, LinkerFlags)) {
return true;
}
}
Expand Down Expand Up @@ -228,6 +246,8 @@ int autolink_extract_main(ArrayRef<const char *> Args, const char *Argv0,
}

std::vector<std::string> LinkerFlags;
// Flags of the form '-lxxx' seen so far
std::unordered_set<std::string> SeenLinkerLibraryFlags;

// Extract the linker flags from the objects.
for (const auto &BinaryFileName : Invocation.getInputFilenames()) {
Expand All @@ -245,7 +265,7 @@ int autolink_extract_main(ArrayRef<const char *> Args, const char *Argv0,
}

if (extractLinkerFlags(BinaryOwner->getBinary(), Instance, BinaryFileName,
LinkerFlags)) {
SeenLinkerLibraryFlags, LinkerFlags)) {
return 1;
}
}
Expand Down
8 changes: 7 additions & 1 deletion test/AutolinkExtract/import.swift
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Original file line number Diff line number Diff line change
@@ -1,10 +1,16 @@
// RUN: %empty-directory(%t)
// RUN: %target-swiftc_driver -emit-module -emit-module-path %t/empty.swiftmodule -module-name empty -module-link-name empty %S/empty.swift
// RUN: %target-swiftc_driver -c %s -I %t -o %t/import_experimental.o
// RUN: %target-swift-autolink-extract %t/import_experimental.o -o - | %FileCheck --check-prefix CHECK-%target-object-format %s
// RUN: %target-swiftc_driver -c %s -I %t -o %t/import_experimental_again.o
// RUN: %target-swift-autolink-extract %t/import_experimental.o %t/import_experimental_again.o -o - | %FileCheck --check-prefix CHECK-%target-object-format %s

// RUN: %target-swift-autolink-extract %t/import_experimental.o %t/import_experimental_again.o -o - | %FileCheck --check-prefix UNIQUE %s

// REQUIRES: autolink-extract

// UNIQUE-COUNT-1: -lempty
// UNIQUE-COUNT-1: -lswiftCore

// CHECK-elf-DAG: -lswiftCore
// CHECK-elf-DAG: -lempty

Expand Down