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[clang][modules] Avoid re-exporting PCH imports on every later module import
We only want to make PCH imports visible once for the the TU, not repeatedly after every subsequent import. This causes some incorrect behaviour with submodule visibility, and causes us to get extra module dependencies in the scanner. So far I have only seen obviously incorrect behaviour when building with -fmodule-name to cause a submodule to be textually included when using the PCH, though the old behaviour seems wrong regardless. rdar://107449644 Differential Revision: https://reviews.llvm.org/D148176
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‎clang/include/clang/Serialization/ASTReader.h

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -948,8 +948,14 @@ class ASTReader
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949949
private:
950950
/// A list of modules that were imported by precompiled headers or
951-
/// any other non-module AST file.
952-
SmallVector<ImportedSubmodule, 2> ImportedModules;
951+
/// any other non-module AST file and have not yet been made visible. If a
952+
/// module is made visible in the ASTReader, it will be transfered to
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/// \c PendingImportedModulesSema.
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SmallVector<ImportedSubmodule, 2> PendingImportedModules;
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/// A list of modules that were imported by precompiled headers or
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/// any other non-module AST file and have not yet been made visible for Sema.
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SmallVector<ImportedSubmodule, 2> PendingImportedModulesSema;
953959
//@}
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955961
/// The system include root to be used when loading the

‎clang/lib/Serialization/ASTReader.cpp

Lines changed: 10 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -3728,7 +3728,7 @@ llvm::Error ASTReader::ReadASTBlock(ModuleFile &F,
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unsigned GlobalID = getGlobalSubmoduleID(F, Record[I++]);
37293729
SourceLocation Loc = ReadSourceLocation(F, Record, I);
37303730
if (GlobalID) {
3731-
ImportedModules.push_back(ImportedSubmodule(GlobalID, Loc));
3731+
PendingImportedModules.push_back(ImportedSubmodule(GlobalID, Loc));
37323732
if (DeserializationListener)
37333733
DeserializationListener->ModuleImportRead(GlobalID, Loc);
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}
@@ -4445,8 +4445,8 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
44454445
UnresolvedModuleRefs.clear();
44464446

44474447
if (Imported)
4448-
Imported->append(ImportedModules.begin(),
4449-
ImportedModules.end());
4448+
Imported->append(PendingImportedModules.begin(),
4449+
PendingImportedModules.end());
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44514451
// FIXME: How do we load the 'use'd modules? They may not be submodules.
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// Might be unnecessary as use declarations are only used to build the
@@ -5050,7 +5050,7 @@ void ASTReader::InitializeContext() {
50505050

50515051
// Re-export any modules that were imported by a non-module AST file.
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// FIXME: This does not make macro-only imports visible again.
5053-
for (auto &Import : ImportedModules) {
5053+
for (auto &Import : PendingImportedModules) {
50545054
if (Module *Imported = getSubmodule(Import.ID)) {
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makeModuleVisible(Imported, Module::AllVisible,
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/*ImportLoc=*/Import.ImportLoc);
@@ -5060,6 +5060,10 @@ void ASTReader::InitializeContext() {
50605060
// nullptr here, we do the same later, in UpdateSema().
50615061
}
50625062
}
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// Hand off these modules to Sema.
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PendingImportedModulesSema.append(PendingImportedModules);
5066+
PendingImportedModules.clear();
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}
50645068

50655069
void ASTReader::finalizeForWriting() {
@@ -8105,13 +8109,14 @@ void ASTReader::UpdateSema() {
81058109
}
81068110

81078111
// For non-modular AST files, restore visiblity of modules.
8108-
for (auto &Import : ImportedModules) {
8112+
for (auto &Import : PendingImportedModulesSema) {
81098113
if (Import.ImportLoc.isInvalid())
81108114
continue;
81118115
if (Module *Imported = getSubmodule(Import.ID)) {
81128116
SemaObj->makeModuleVisible(Imported, Import.ImportLoc);
81138117
}
81148118
}
8119+
PendingImportedModulesSema.clear();
81158120
}
81168121

81178122
IdentifierInfo *ASTReader::get(StringRef Name) {

‎clang/test/ClangScanDeps/modules-pch-imports.c

Lines changed: 108 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,108 @@
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// Check that a module from -fmodule-name= does not accidentally pick up extra
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// dependencies that come from a PCH.
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// RUN: rm -rf %t
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// RUN: split-file %s %t
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// RUN: sed "s|DIR|%/t|g" %t/cdb.json.template > %t/cdb.json
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// RUN: sed "s|DIR|%/t|g" %t/cdb_pch.json.template > %t/cdb_pch.json
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// Scan PCH
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// RUN: clang-scan-deps -compilation-database %t/cdb_pch.json \
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// RUN: -format experimental-full -mode preprocess-dependency-directives \
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// RUN: > %t/deps_pch.json
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// Build PCH
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// RUN: %deps-to-rsp %t/deps_pch.json --module-name A > %t/A.rsp
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// RUN: %deps-to-rsp %t/deps_pch.json --module-name B > %t/B.rsp
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// RUN: %deps-to-rsp %t/deps_pch.json --tu-index 0 > %t/pch.rsp
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// RUN: %clang @%t/A.rsp
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// RUN: %clang @%t/B.rsp
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// RUN: %clang @%t/pch.rsp
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// Scan TU with PCH
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// RUN: clang-scan-deps -compilation-database %t/cdb.json \
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// RUN: -format experimental-full -mode preprocess-dependency-directives \
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// RUN: > %t/deps.json
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// RUN: cat %t/deps.json | sed 's:\\\\\?:/:g' | FileCheck %s -DPREFIX=%/t
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// Verify that the only modular import in C is E and not the unrelated modules
30+
// A or B that come from the PCH.
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// CHECK: {
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// CHECK-NEXT: "modules": [
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// CHECK-NEXT: {
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// CHECK: "clang-module-deps": [
36+
// CHECK-NEXT: {
37+
// CHECK: "module-name": "E"
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// CHECK: }
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// CHECK-NEXT: ]
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// CHECK: "clang-modulemap-file": "[[PREFIX]]/module.modulemap"
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// CHECK: "command-line": [
42+
// CHECK-NOT: "-fmodule-file=
43+
// CHECK: "-fmodule-file={{(E=)?}}[[PREFIX]]/{{.*}}/E-{{.*}}.pcm"
44+
// CHECK-NOT: "-fmodule-file=
45+
// CHECK: ]
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// CHECK: "name": "C"
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// CHECK: }
48+
49+
50+
//--- cdb_pch.json.template
51+
[{
52+
"file": "DIR/prefix.h",
53+
"directory": "DIR",
54+
"command": "clang -x c-header DIR/prefix.h -o DIR/prefix.h.pch -fmodules -fimplicit-modules -fimplicit-module-maps -fmodules-cache-path=DIR/module-cache"
55+
}]
56+
57+
//--- cdb.json.template
58+
[{
59+
"file": "DIR/tu.c",
60+
"directory": "DIR",
61+
"command": "clang -fsyntax-only DIR/tu.c -include DIR/prefix.h -fmodule-name=C -fmodules -fimplicit-modules -fimplicit-module-maps -fmodules-cache-path=DIR/module-cache"
62+
}]
63+
64+
//--- module.modulemap
65+
module A { header "A.h" export * }
66+
module B { header "B.h" export * }
67+
module C { header "C.h" export * }
68+
module D { header "D.h" export * }
69+
module E { header "E.h" export * }
70+
71+
//--- A.h
72+
#pragma once
73+
struct A { int x; };
74+
75+
//--- B.h
76+
#pragma once
77+
#include "A.h"
78+
struct B { struct A a; };
79+
80+
//--- C.h
81+
#pragma once
82+
#include "E.h"
83+
struct C { struct E e; };
84+
85+
//--- D.h
86+
#pragma once
87+
#include "C.h"
88+
struct D { struct C c; };
89+
90+
//--- E.h
91+
#pragma once
92+
struct E { int y; };
93+
94+
//--- prefix.h
95+
#include "B.h"
96+
97+
//--- tu.c
98+
// C.h is first included textually due to -fmodule-name=C.
99+
#include "C.h"
100+
// importing D pulls in a modular import of C; it's this build of C that we
101+
// are verifying above
102+
#include "D.h"
103+
104+
void tu(void) {
105+
struct A a;
106+
struct B b;
107+
struct C c;
108+
}

‎clang/test/Modules/submodule-visibility-pch.c

Lines changed: 56 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,56 @@
1+
// Verify that the use of a PCH does not accidentally make modules from the PCH
2+
// visible to submodules when using -fmodules-local-submodule-visibility
3+
// and -fmodule-name to trigger a textual include.
4+
5+
// RUN: rm -rf %t
6+
// RUN: split-file %s %t
7+
8+
// First check that it works with a header
9+
10+
// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t/cache \
11+
// RUN: -fmodules-local-submodule-visibility -fimplicit-module-maps \
12+
// RUN: -fmodule-name=Mod \
13+
// RUN: %t/tu.c -include %t/prefix.h -I %t -verify
14+
15+
// Now with a PCH
16+
17+
// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t/cache \
18+
// RUN: -fmodules-local-submodule-visibility -fimplicit-module-maps \
19+
// RUN: -x c-header %t/prefix.h -emit-pch -o %t/prefix.pch -I %t
20+
21+
// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t/cache \
22+
// RUN: -fmodules-local-submodule-visibility -fimplicit-module-maps \
23+
// RUN: -fmodule-name=Mod \
24+
// RUN: %t/tu.c -include-pch %t/prefix.pch -I %t -verify
25+
26+
//--- module.modulemap
27+
module ModViaPCH { header "ModViaPCH.h" }
28+
module ModViaInclude { header "ModViaInclude.h" }
29+
module Mod { header "Mod.h" }
30+
module SomeOtherMod { header "SomeOtherMod.h" }
31+
32+
//--- ModViaPCH.h
33+
#define ModViaPCH 1
34+
35+
//--- ModViaInclude.h
36+
#define ModViaInclude 2
37+
38+
//--- SomeOtherMod.h
39+
// empty
40+
41+
//--- Mod.h
42+
#include "SomeOtherMod.h"
43+
#ifdef ModViaPCH
44+
#error "Visibility violation ModViaPCH"
45+
#endif
46+
#ifdef ModViaInclude
47+
#error "Visibility violation ModViaInclude"
48+
#endif
49+
50+
//--- prefix.h
51+
#include "ModViaPCH.h"
52+
53+
//--- tu.c
54+
#include "ModViaInclude.h"
55+
#include "Mod.h"
56+
// expected-no-diagnostics

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