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[clang-tidy] Fix a crash in bugprone-not-null-terminated-result check…
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… when `__STDC_WANT_LIB_EXT1__` was undefined after definition.

PP->getMacroInfo() returns nullptr for undefined macro, so we need to check this return value before dereference.
Stack dump:
```
 #0 0x0000000002185e6a llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/llvm-project/build/bin/clang-tidy+0x2185e6a)
 #1 0x0000000002183e8c llvm::sys::RunSignalHandlers() (/llvm-project/build/bin/clang-tidy+0x2183e8c)
 #2 0x0000000002183ff3 SignalHandler(int) (/llvm-project/build/bin/clang-tidy+0x2183ff3)
 #3 0x00007f37df9b1390 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x11390)
 #4 0x000000000052054e clang::tidy::bugprone::NotNullTerminatedResultCheck::check(clang::ast_matchers::MatchFinder::MatchResult const&) (/llvm-project/build/bin/clang-tidy+0x52054e)
```

Reviewed By: hokein

Differential Revision: https://reviews.llvm.org/D85523
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ArcsinX committed Aug 10, 2020
1 parent 626d0f5 commit 5965fbf
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Showing 2 changed files with 25 additions and 5 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -802,11 +802,14 @@ void NotNullTerminatedResultCheck::check(
while (It != PP->macro_end() && !AreSafeFunctionsWanted.hasValue()) {
if (It->first->getName() == "__STDC_WANT_LIB_EXT1__") {
const auto *MI = PP->getMacroInfo(It->first);
const auto &T = MI->tokens().back();
StringRef ValueStr = StringRef(T.getLiteralData(), T.getLength());
llvm::APInt IntValue;
ValueStr.getAsInteger(10, IntValue);
AreSafeFunctionsWanted = IntValue.getZExtValue();
// PP->getMacroInfo() returns nullptr if macro has no definition.
if (MI) {
const auto &T = MI->tokens().back();
StringRef ValueStr = StringRef(T.getLiteralData(), T.getLength());
llvm::APInt IntValue;
ValueStr.getAsInteger(10, IntValue);
AreSafeFunctionsWanted = IntValue.getZExtValue();
}
}

++It;
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
// RUN: %check_clang_tidy %s bugprone-not-null-terminated-result %t -- \
// RUN: -- -std=c11 -I %S/Inputs/bugprone-not-null-terminated-result

#include "not-null-terminated-result-c.h"

#define __STDC_LIB_EXT1__ 1
#define __STDC_WANT_LIB_EXT1__ 1
#undef __STDC_WANT_LIB_EXT1__

void f(const char *src) {
char dest[13];
memcpy_s(dest, 13, src, strlen(src) - 1);
// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: the result from calling 'memcpy_s' is not null-terminated [bugprone-not-null-terminated-result]
// CHECK-FIXES: char dest[14];
// CHECK-FIXES-NEXT: strncpy_s(dest, 14, src, strlen(src) - 1);
}

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