[LLD][COFF] Fix ordering of CRT global initializers in COMDAT sections
(patch by Benoit Rousseau)
This patch fixes a bug where the global variable initializers were sometimes not invoked in the correct order when it involved a C++ template instantiation.
Differential Revision: https://reviews.llvm.org/D52749
git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@343847 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/COFF/Chunks.cpp b/COFF/Chunks.cpp
index eb90bd7..5fb33e1 100644
--- a/COFF/Chunks.cpp
+++ b/COFF/Chunks.cpp
@@ -590,6 +590,13 @@
Other->Live = false;
}
+uint32_t SectionChunk::getSectionNumber() const {
+ DataRefImpl R;
+ R.p = reinterpret_cast<uintptr_t>(Header);
+ SectionRef S(R, File->getCOFFObj());
+ return S.getIndex() + 1;
+}
+
CommonChunk::CommonChunk(const COFFSymbolRef S) : Sym(S) {
// Common symbols are aligned on natural boundaries up to 32 bytes.
// This is what MSVC link.exe does.
diff --git a/COFF/Chunks.h b/COFF/Chunks.h
index e9facb8..bdfff7c 100644
--- a/COFF/Chunks.h
+++ b/COFF/Chunks.h
@@ -203,10 +203,13 @@
// Allow iteration over the associated child chunks for this section.
ArrayRef<SectionChunk *> children() const { return AssocChildren; }
+ // The section ID this chunk belongs to in its Obj.
+ uint32_t getSectionNumber() const;
+
// A pointer pointing to a replacement for this chunk.
// Initially it points to "this" object. If this chunk is merged
// with other chunk by ICF, it points to another chunk,
- // and this chunk is considrered as dead.
+ // and this chunk is considered as dead.
SectionChunk *Repl;
// The CRC of the contents as described in the COFF spec 4.5.5.
diff --git a/COFF/Writer.cpp b/COFF/Writer.cpp
index 23de466..d42c82c 100644
--- a/COFF/Writer.cpp
+++ b/COFF/Writer.cpp
@@ -192,6 +192,7 @@
void writeSections();
void writeBuildId();
void sortExceptionTable();
+ void sortCRTSectionChunks(std::vector<Chunk *> &Chunks);
llvm::Optional<coff_symbol16> createSymbol(Defined *D);
size_t addEntryToStringTable(StringRef Str);
@@ -732,13 +733,18 @@
StringRef Name = getOutputSectionName(Pair.first.first);
uint32_t OutChars = Pair.first.second;
- // In link.exe, there is a special case for the I386 target where .CRT
- // sections are treated as if they have output characteristics DATA | R if
- // their characteristics are DATA | R | W. This implements the same special
- // case for all architectures.
- if (Name == ".CRT")
+ if (Name == ".CRT") {
+ // In link.exe, there is a special case for the I386 target where .CRT
+ // sections are treated as if they have output characteristics DATA | R if
+ // their characteristics are DATA | R | W. This implements the same
+ // special case for all architectures.
OutChars = DATA | R;
+ log("Processing section " + Pair.first.first + " -> " + Name);
+
+ sortCRTSectionChunks(Pair.second);
+ }
+
OutputSection *Sec = CreateSection(Name, OutChars);
std::vector<Chunk *> &Chunks = Pair.second;
for (Chunk *C : Chunks)
@@ -1577,6 +1583,42 @@
errs() << "warning: don't know how to handle .pdata.\n";
}
+// The CRT section contains, among other things, the array of function
+// pointers that initialize every global variable that is not trivially
+// constructed. The CRT calls them one after the other prior to invoking
+// main().
+//
+// As per C++ spec, 3.6.2/2.3,
+// "Variables with ordered initialization defined within a single
+// translation unit shall be initialized in the order of their definitions
+// in the translation unit"
+//
+// It is therefore critical to sort the chunks containing the function
+// pointers in the order that they are listed in the object file (top to
+// bottom), otherwise global objects might not be initialized in the
+// correct order.
+void Writer::sortCRTSectionChunks(std::vector<Chunk *> &Chunks) {
+ auto SectionChunkOrder = [](const Chunk *A, const Chunk *B) {
+ auto SA = dyn_cast<SectionChunk>(A);
+ auto SB = dyn_cast<SectionChunk>(B);
+ assert(SA && SB && "Non-section chunks in CRT section!");
+
+ StringRef SAObj = SA->File->MB.getBufferIdentifier();
+ StringRef SBObj = SB->File->MB.getBufferIdentifier();
+
+ return SAObj == SBObj && SA->getSectionNumber() < SB->getSectionNumber();
+ };
+ std::stable_sort(Chunks.begin(), Chunks.end(), SectionChunkOrder);
+
+ if (Config->Verbose) {
+ for (auto &C : Chunks) {
+ auto SC = dyn_cast<SectionChunk>(C);
+ log(" " + SC->File->MB.getBufferIdentifier().str() +
+ ", SectionID: " + Twine(SC->getSectionNumber()));
+ }
+ }
+}
+
OutputSection *Writer::findSection(StringRef Name) {
for (OutputSection *Sec : OutputSections)
if (Sec->Name == Name)
diff --git a/test/COFF/Inputs/crt-dyn-initializer-order_1.yaml b/test/COFF/Inputs/crt-dyn-initializer-order_1.yaml
new file mode 100644
index 0000000..302f6f2
--- /dev/null
+++ b/test/COFF/Inputs/crt-dyn-initializer-order_1.yaml
@@ -0,0 +1,15 @@
+--- !COFF
+header:
+ Machine: IMAGE_FILE_MACHINE_AMD64
+ Characteristics: [ ]
+sections:
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 55
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 70
+symbols:
+...
diff --git a/test/COFF/Inputs/crt-dyn-initializer-order_2.yaml b/test/COFF/Inputs/crt-dyn-initializer-order_2.yaml
new file mode 100644
index 0000000..a2d0e5e
--- /dev/null
+++ b/test/COFF/Inputs/crt-dyn-initializer-order_2.yaml
@@ -0,0 +1,19 @@
+--- !COFF
+header:
+ Machine: IMAGE_FILE_MACHINE_AMD64
+ Characteristics: [ ]
+sections:
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 10
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 11
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 12
+symbols:
+...
diff --git a/test/COFF/crt-dyn-initializer-order.test b/test/COFF/crt-dyn-initializer-order.test
new file mode 100644
index 0000000..963b065
--- /dev/null
+++ b/test/COFF/crt-dyn-initializer-order.test
@@ -0,0 +1,100 @@
+# // a.cpp
+# #include <iostream>
+# #include <vector>
+#
+# template <int Magic> struct TemplatedObject {
+# static std::vector<TemplatedObject<Magic> *> Instances;
+# TemplatedObject() { Instances.push_back(this); }
+# };
+#
+# using Object = TemplatedObject<0>;
+# template <> std::vector<Object *> Object::Instances{};
+# Object idle{};
+#
+# int main() {
+# if (Object::Instances.size() == 0)
+# std::cout << "It's broken" << std::endl;
+# else
+# std::cout << "It works!" << std::endl;
+# return 0;
+# }
+# // using `clang-cl /c a.cpp | lld-link a.obj` works
+# // using `cl /c a.cpp | lld-link a.obj` fails without lld/COFF/Writer.cpp/Writer::sortSectionChunks()
+
+# RUN: yaml2obj %s > %t.obj
+# RUN: yaml2obj %S/Inputs/crt-dyn-initializer-order_1.yaml > %t1.obj
+# RUN: yaml2obj %S/Inputs/crt-dyn-initializer-order_2.yaml > %t2.obj
+
+# CHECK: Name: .CRT
+# CHECK: Characteristics [
+# CHECK-NEXT: IMAGE_SCN_CNT_INITIALIZED_DATA
+# CHECK-NEXT: IMAGE_SCN_MEM_READ
+# CHECK-NEXT: ]
+# CHECK-NEXT: SectionData (
+
+# RUN: lld-link /out:%t.dll /entry:__ImageBase /dll %t.obj %t1.obj %t2.obj
+# RUN: llvm-readobj -sections -section-data %t.dll | FileCheck %s --check-prefixes CHECK,CASE1
+# CASE1-NEXT: 01020304 55701011 1205
+
+# RUN: lld-link /out:%t.dll /entry:__ImageBase /dll %t.obj %t2.obj %t1.obj
+# RUN: llvm-readobj -sections -section-data %t.dll | FileCheck %s --check-prefixes CHECK,CASE2
+# CASE2-NEXT: 01020304 10111255 7005
+
+# RUN: lld-link /out:%t.dll /entry:__ImageBase /dll %t1.obj %t2.obj %t.obj
+# RUN: llvm-readobj -sections -section-data %t.dll | FileCheck %s --check-prefixes CHECK,CASE3
+# CASE3-NEXT: 01557010 11120203 0405
+
+# RUN: lld-link /out:%t.dll /entry:__ImageBase /dll %t1.obj %t.obj %t2.obj
+# RUN: llvm-readobj -sections -section-data %t.dll | FileCheck %s --check-prefixes CHECK,CASE4
+# CASE4-NEXT: 01557002 03041011 1205
+
+# RUN: lld-link /out:%t.dll /entry:__ImageBase /dll %t2.obj %t1.obj %t.obj
+# RUN: llvm-readobj -sections -section-data %t.dll | FileCheck %s --check-prefixes CHECK,CASE5
+# CASE5-NEXT: 01101112 55700203 0405
+
+# RUN: lld-link /out:%t.dll /entry:__ImageBase /dll %t2.obj %t.obj %t1.obj
+# RUN: llvm-readobj -sections -section-data %t.dll | FileCheck %s --check-prefixes CHECK,CASE6
+# CASE6-NEXT: 01101112 02030455 7005
+
+# CHECK-NEXT: )
+
+--- !COFF
+header:
+ Machine: IMAGE_FILE_MACHINE_AMD64
+ Characteristics: [ ]
+sections:
+ - Name: '.CRT$XCA'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 01
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 02
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_LNK_COMDAT ]
+ Alignment: 1
+ SectionData: 03
+ - Name: '.CRT$XCU'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 04
+ - Name: '.CRT$XCZ'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ SectionData: 05
+symbols:
+ - Name: '.CRT$XCU'
+ Value: 0
+ SectionNumber: 3
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+ SectionDefinition:
+ Length: 1
+ NumberOfRelocations: 0
+ NumberOfLinenumbers: 0
+ CheckSum: 1
+ Number: 2
+ Selection: IMAGE_COMDAT_SELECT_ASSOCIATIVE
+...
