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Refs #9173: Fix FN bufferAccessOutOfBounds (memset on array, &a[0]) #8656

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Refs #9173: Fix FN bufferAccessOutOfBounds (memset on array, &a[0]) #8656

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f70a8b2
Update checkbufferoverrun.cpp
chrchr-github Jun 17, 2026
4233c6c
Update testbufferoverrun.cpp
chrchr-github Jun 17, 2026
b5bd734
Update checkbufferoverrun.cpp
chrchr-github Jun 17, 2026
ca719a2
Update checkbufferoverrun.cpp
chrchr-github Jun 17, 2026
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10 changes: 9 additions & 1 deletion lib/checkbufferoverrun.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -556,8 +556,16 @@ ValueFlow::Value CheckBufferOverrunImpl::getBufferSize(const Token *bufTok) cons
{
if (!bufTok->valueType())
return ValueFlow::Value(-1);
if (bufTok->isUnaryOp("&"))

if (bufTok->isUnaryOp("&")) {
bufTok = bufTok->astOperand1();
if (Token::simpleMatch(bufTok, "[")) {
const Token* index = bufTok->astOperand2();
if (!(index && index->hasKnownIntValue() && index->getKnownIntValue() == 0))
return ValueFlow::Value(-1);
bufTok = bufTok->astOperand1();
}
}
const Variable *var = bufTok->variable();

if (!var || var->dimensions().empty()) {
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34 changes: 34 additions & 0 deletions test/testbufferoverrun.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,7 @@ class TestBufferOverrun : public TestFixture {
TEST_CASE(buffer_overrun_35); //#2304
TEST_CASE(buffer_overrun_36);
TEST_CASE(buffer_overrun_37);
TEST_CASE(buffer_overrun_38);
TEST_CASE(buffer_overrun_errorpath);
TEST_CASE(buffer_overrun_bailoutIfSwitch); // ticket #2378 : bailoutIfSwitch
TEST_CASE(buffer_overrun_function_array_argument);
Expand Down Expand Up @@ -3507,6 +3508,39 @@ class TestBufferOverrun : public TestFixture {
ASSERT_EQUALS("", errout_str());
}

void buffer_overrun_38() { // #9173
check("void f() {\n"
" int a[10];\n"
" memset(&a[0], 0, 20 * sizeof(int));\n"
"}\n"
"void g() {\n"
" int a[10];\n"
" memset(&a[0], 0, 10 * sizeof(int));\n"
"}\n"
"void h() {\n"
" int a[10];\n"
" memset(&a[5], 0, 5 * sizeof(int));\n"
"}\n"
"void i() {\n"
" int a[10][10];\n"
" memset(&a[0][0], 0, 100 * sizeof(int));\n"
"}\n");
ASSERT_EQUALS("[test.cpp:3:12]: (error) Buffer is accessed out of bounds: &a[0] [bufferAccessOutOfBounds]\n", errout_str());

check("void f() {\n"
" int a[10];\n"
" memset(&a[5], 0, 10 * sizeof(int));\n"
"}\n"
"void g() {\n"
" int a[1][1];\n"
" memset(&a[0][0], 0, 10 * sizeof(int));\n"
"}\n");
TODO_ASSERT_EQUALS("[test.cpp:3:12]: (error) Buffer is accessed out of bounds: &a[5] [bufferAccessOutOfBounds]\n"
"[test.cpp:7:12]: (error) Buffer is accessed out of bounds: &a[0][0] [bufferAccessOutOfBounds]\n",
"",
errout_str());
}

void buffer_overrun_errorpath() {
setMultiline();
Settings s = settings0;
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