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[clang][DependencyScanner] Remove all warning flags when suppressing warnings (llvm#71612)
Since system modules don't emit most warnings, remove the warning flags to increase module reuse.
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4 files changed

+155
-2
lines changed

4 files changed

+155
-2
lines changed

‎clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -51,8 +51,11 @@ enum class ScanningOptimizations {
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/// Remove unused header search paths including header maps.
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HeaderSearch = 1,
5353

54-
LLVM_MARK_AS_BITMASK_ENUM(HeaderSearch),
55-
All = HeaderSearch,
54+
/// Remove warnings from system modules.
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SystemWarnings = 2,
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LLVM_MARK_AS_BITMASK_ENUM(SystemWarnings),
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All = HeaderSearch | SystemWarnings,
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Default = All
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};
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‎clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -52,6 +52,28 @@ static void optimizeHeaderSearchOpts(HeaderSearchOptions &Opts,
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Opts.UserEntries.push_back(Entries[Idx]);
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}
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55+
static void optimizeDiagnosticOpts(DiagnosticOptions &Opts,
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bool IsSystemModule) {
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// If this is not a system module or -Wsystem-headers was passed, don't
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// optimize.
59+
if (!IsSystemModule)
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return;
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bool Wsystem_headers = false;
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for (StringRef Opt : Opts.Warnings) {
63+
bool isPositive = !Opt.consume_front("no-");
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if (Opt == "system-headers")
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Wsystem_headers = isPositive;
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}
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if (Wsystem_headers)
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return;
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// Remove all warning flags. System modules suppress most, but not all,
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// warnings.
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Opts.Warnings.clear();
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Opts.UndefPrefixes.clear();
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Opts.Remarks.clear();
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}
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static std::vector<std::string> splitString(std::string S, char Separator) {
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SmallVector<StringRef> Segments;
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StringRef(S).split(Segments, Separator, /*MaxSplit=*/-1, /*KeepEmpty=*/false);
@@ -532,6 +554,10 @@ ModuleDepCollectorPP::handleTopLevelModule(const Module *M) {
532554
if (any(MDC.OptimizeArgs & ScanningOptimizations::HeaderSearch))
533555
optimizeHeaderSearchOpts(BuildInvocation.getMutHeaderSearchOpts(),
534556
*MDC.ScanInstance.getASTReader(), *MF);
557+
if (any(MDC.OptimizeArgs & ScanningOptimizations::SystemWarnings))
558+
optimizeDiagnosticOpts(
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BuildInvocation.getMutDiagnosticOpts(),
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BuildInvocation.getFrontendOpts().IsSystemModule);
535561
});
536562

537563
MDC.associateWithContextHash(CI, MD);

‎clang/test/ClangScanDeps/optimize-system-warnings.m

Lines changed: 123 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,123 @@
1+
// This test verifies that system module variants are mergable despite having
2+
// different warning flags, as most warnings are disabled in system modules.
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// This checks for system modules marked as such both via `-isystem` and
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// `[system]`.
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// RUN: rm -rf %t
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// RUN: split-file %s %t
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// RUN: sed -e "s|DIR|%/t|g" %t/build/compile-commands.json.in > %t/build/compile-commands.json
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// RUN: clang-scan-deps -compilation-database %t/build/compile-commands.json \
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// RUN: -j 1 -format experimental-full -optimize-args=system-warnings > %t/deps.db
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// RUN: cat %t/deps.db | sed 's:\\\\\?:/:g' | FileCheck %s -DPREFIX=%/t
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// CHECK: {
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// CHECK-NEXT: "modules": [
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// CHECK-NEXT: {
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// CHECK-NEXT: "clang-module-deps": [],
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// CHECK-NEXT: "clang-modulemap-file":
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// CHECK-NEXT: "command-line": [
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// CHECK-NOT: "-W
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// CHECK: ],
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// CHECK-NEXT: "context-hash": "{{.*}}",
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// CHECK-NEXT: "file-deps": [
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// CHECK: ],
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// CHECK-NEXT: "name": "A"
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// CHECK-NEXT: },
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// CHECK-NEXT: {
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// CHECK-NEXT: "clang-module-deps": [],
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// CHECK-NEXT: "clang-modulemap-file":
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// CHECK-NEXT: "command-line": [
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// CHECK-NOT: "-W
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// CHECK: ],
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// CHECK-NEXT: "context-hash": "{{.*}}",
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// CHECK-NEXT: "file-deps": [
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// CHECK: ],
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// CHECK-NEXT: "name": "B"
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// CHECK-NEXT: },
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// CHECK-NEXT: {
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// CHECK-NEXT: "clang-module-deps": [],
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// CHECK-NEXT: "clang-modulemap-file":
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// CHECK-NEXT: "command-line": [
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// CHECK: "-Wmaybe-unused
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// CHECK: ],
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// CHECK-NEXT: "context-hash": "{{.*}}",
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// CHECK-NEXT: "file-deps": [
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// CHECK: ],
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// CHECK-NEXT: "name": "C"
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// CHECK-NEXT: }
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// CHECK-NEXT: ],
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// CHECK-NEXT: "translation-units": [
50+
// CHECK: ]
51+
// CHECK: }
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53+
// A.m and B.m verify that system modules with different warning flags get
54+
// merged. C.m verifies that -Wsystem-headers disables the optimization.
55+
//--- build/compile-commands.json.in
56+
57+
[
58+
{
59+
"directory": "DIR",
60+
"command": "clang -c DIR/A.m -isystem modules/A -I modules/B -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-module-maps",
61+
"file": "DIR/A.m"
62+
},
63+
{
64+
"directory": "DIR",
65+
"command": "clang -c DIR/B.m -isystem modules/A -I modules/B -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-module-maps -Wmaybe-unused",
66+
"file": "DIR/B.m"
67+
},
68+
{
69+
"directory": "DIR",
70+
"command": "clang -c DIR/C.m -isystem modules/C -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-module-maps -Wmaybe-unused -Wsystem-headers",
71+
"file": "DIR/C.m"
72+
}
73+
]
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75+
//--- modules/A/module.modulemap
76+
77+
module A {
78+
umbrella header "A.h"
79+
}
80+
81+
//--- modules/A/A.h
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typedef int A_t;
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85+
//--- modules/B/module.modulemap
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module B [system] {
88+
umbrella header "B.h"
89+
}
90+
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//--- modules/B/B.h
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typedef int B_t;
94+
95+
//--- modules/C/module.modulemap
96+
97+
module C [system] {
98+
umbrella header "C.h"
99+
}
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101+
//--- modules/C/C.h
102+
103+
typedef int C_t;
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105+
//--- A.m
106+
107+
#include <A.h>
108+
#include <B.h>
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110+
A_t a = 0;
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112+
//--- B.m
113+
114+
#include <A.h>
115+
#include <B.h>
116+
117+
A_t b = 0;
118+
119+
//--- C.m
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#include <C.h>
122+
123+
C_t c = 0;

‎clang/tools/clang-scan-deps/ClangScanDeps.cpp

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -156,6 +156,7 @@ static void ParseArgs(int argc, char **argv) {
156156
llvm::StringSwitch<std::optional<ScanningOptimizations>>(Arg)
157157
.Case("none", ScanningOptimizations::None)
158158
.Case("header-search", ScanningOptimizations::HeaderSearch)
159+
.Case("system-warnings", ScanningOptimizations::SystemWarnings)
159160
.Case("all", ScanningOptimizations::All)
160161
.Default(std::nullopt);
161162
if (!Optimization) {

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