[LLD][COFF] Allow symbols with empty chunks to have no associated output section in the PDB writer #149523
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…put section If a chunk is empty and there are no other non-empty chunks in the same section, removeEmptySections() will remove the entire section. In this case, use a section index of 0, as the MSVC linker does, instead of asserting.
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This issue was reported to cause problems when building Wine: In that case, it involved the recently introduced |
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@llvm/pr-subscribers-lld-coff @llvm/pr-subscribers-platform-windows Author: Jacek Caban (cjacek) ChangesIf a chunk is empty and there are no other non-empty chunks in the same section, Full diff: https://github.com/llvm/llvm-project/pull/149523.diff 2 Files Affected:
diff --git a/lld/COFF/PDB.cpp b/lld/COFF/PDB.cpp
index a54ea403ba2ec..94eeae2797971 100644
--- a/lld/COFF/PDB.cpp
+++ b/lld/COFF/PDB.cpp
@@ -1135,9 +1135,12 @@ static pdb::BulkPublic createPublic(COFFLinkerContext &ctx, Defined *def) {
pub.setFlags(flags);
OutputSection *os = ctx.getOutputSection(def->getChunk());
- assert(os && "all publics should be in final image");
- pub.Offset = def->getRVA() - os->getRVA();
- pub.Segment = os->sectionIndex;
+ assert((os || !def->getChunk()->getSize()) &&
+ "all publics should be in final image");
+ if (os) {
+ pub.Offset = def->getRVA() - os->getRVA();
+ pub.Segment = os->sectionIndex;
+ }
return pub;
}
diff --git a/lld/test/COFF/pdb-empty-sec.s b/lld/test/COFF/pdb-empty-sec.s
new file mode 100644
index 0000000000000..0d61447b76651
--- /dev/null
+++ b/lld/test/COFF/pdb-empty-sec.s
@@ -0,0 +1,19 @@
+// REQUIRES: x86
+
+// RUN: llvm-mc -filetype=obj -triple=x86_64-windows %s -o %t.obj
+// RUN: lld-link -dll -noentry -debug %t.obj -out:%t.dll
+// RUN: llvm-pdbutil dump -publics %t.pdb | FileCheck %s
+
+// CHECK: Records
+// CHECK-NEXT: 0 | S_PUB32 [size = 20] `func`
+// CHECK-NEXT: flags = none, addr = 0001:0000
+// CHECK-NEXT: 20 | S_PUB32 [size = 20] `sym`
+// CHECK-NEXT: flags = none, addr = 0000:0000
+
+ .globl sym
+ .data
+sym:
+ .text
+ .globl func
+func:
+ ret
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@llvm/pr-subscribers-lld Author: Jacek Caban (cjacek) ChangesIf a chunk is empty and there are no other non-empty chunks in the same section, Full diff: https://github.com/llvm/llvm-project/pull/149523.diff 2 Files Affected:
diff --git a/lld/COFF/PDB.cpp b/lld/COFF/PDB.cpp
index a54ea403ba2ec..94eeae2797971 100644
--- a/lld/COFF/PDB.cpp
+++ b/lld/COFF/PDB.cpp
@@ -1135,9 +1135,12 @@ static pdb::BulkPublic createPublic(COFFLinkerContext &ctx, Defined *def) {
pub.setFlags(flags);
OutputSection *os = ctx.getOutputSection(def->getChunk());
- assert(os && "all publics should be in final image");
- pub.Offset = def->getRVA() - os->getRVA();
- pub.Segment = os->sectionIndex;
+ assert((os || !def->getChunk()->getSize()) &&
+ "all publics should be in final image");
+ if (os) {
+ pub.Offset = def->getRVA() - os->getRVA();
+ pub.Segment = os->sectionIndex;
+ }
return pub;
}
diff --git a/lld/test/COFF/pdb-empty-sec.s b/lld/test/COFF/pdb-empty-sec.s
new file mode 100644
index 0000000000000..0d61447b76651
--- /dev/null
+++ b/lld/test/COFF/pdb-empty-sec.s
@@ -0,0 +1,19 @@
+// REQUIRES: x86
+
+// RUN: llvm-mc -filetype=obj -triple=x86_64-windows %s -o %t.obj
+// RUN: lld-link -dll -noentry -debug %t.obj -out:%t.dll
+// RUN: llvm-pdbutil dump -publics %t.pdb | FileCheck %s
+
+// CHECK: Records
+// CHECK-NEXT: 0 | S_PUB32 [size = 20] `func`
+// CHECK-NEXT: flags = none, addr = 0001:0000
+// CHECK-NEXT: 20 | S_PUB32 [size = 20] `sym`
+// CHECK-NEXT: flags = none, addr = 0000:0000
+
+ .globl sym
+ .data
+sym:
+ .text
+ .globl func
+func:
+ ret
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cjacek
referenced
this pull request
in mstorsjo/llvm-mingw
Jul 18, 2025
Relevant changes include: - Lots of work for supporting ARM64EC and ARM64X - LLD now produces more compact string tables in executables (only relevant when including debug symbols) - llvm-rc now supports multiplication/division expressions, like GNU windres - Improved support for armv7 and aarch64 in libunwind (for Itanium ABI "forced unwinding", which I'm not aware of being used in practice anywhere) - Made the libunwind, libcxxabi, libcxx and compiler-rt tests pass on armv7 and aarch64 mingw - Made the llvm/clang tests pass on aarch64 mingw
mstorsjo
approved these changes
Jul 28, 2025
There was a problem hiding this comment.
LGTM, thanks.
(It may be nice to mention "PDB" somewhere in the commit message too.)
Also for added context, this should be backported to 21.x, as this fixes a regression since f66f2fe in one build configuration, as reported in mstorsjo/llvm-mingw@ae03577#commitcomment-162336778.
cjacek
changed the title
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/cherry-pick 1ab04fc |
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/pull-request #150969 |
tru
pushed a commit
to llvmbot/llvm-project
that referenced
this pull request
Jul 29, 2025
…put section in the PDB writer (llvm#149523) If a chunk is empty and there are no other non-empty chunks in the same section, `removeEmptySections()` will remove the entire section. In this case, use a section index of 0, as the MSVC linker does, instead of asserting. (cherry picked from commit 1ab04fc)
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If a chunk is empty and there are no other non-empty chunks in the same section,
removeEmptySections()will remove the entire section. In this case, use a section index of 0, as the MSVC linker does, instead of asserting.