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fix #11542: FP memleak when using memcpy() with pointer #6792

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fix #11542: FP memleak when using memcpy() with pointer #6792

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22f7c0a
begin checking memcpy/memmove in checkleakautovar
ludviggunne Sep 10, 2024
a117b8d
fix #11542 and add tests
ludviggunne Sep 11, 2024
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48 changes: 48 additions & 0 deletions lib/checkleakautovar.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -363,6 +363,54 @@ bool CheckLeakAutoVar::checkScope(const Token * const startToken,
while (Token::Match(ftok, "%name% :: %name%"))
ftok = ftok->tokAt(2);

// memcpy / memmove
if (Token::Match(varTok, "memcpy|memmove")) {
const std::vector<const Token*> args = getArguments(varTok);
// too few args for memcpy / memmove call
if (args.size() < 3)
continue;
const Token *dst = args[0];
const Token *src = args[1];

// check that dst arg is pointer to pointer
int dstIndirectionLevel = 0;
while (dst->str() == "*") {
dst = dst->astOperand1();
dstIndirectionLevel--;
}
if (dst->str() == "&") {
dst = dst->astOperand1();
dstIndirectionLevel++;
}
if (!dst->isVariable())
continue;
if (dstIndirectionLevel + dst->variable()->valueType()->pointer != 2)
continue;

// check that src arg is pointer to pointer
int srcIndirectionLevel = 0;
while (src->str() == "*") {
src = src->astOperand1();
srcIndirectionLevel--;
}
if (src->str() == "&") {
src = src->astOperand1();
srcIndirectionLevel++;
}
if (!src->isVariable())
continue;
if (srcIndirectionLevel + src->variable()->valueType()->pointer != 2)
continue;

if (!dst->variable()->isArgument()) {
varInfo.alloctype[dst->varId()].status = VarInfo::AllocStatus::ALLOC;
}

// no multivariable checking currently (see assignment below)
// treat source pointer as unallocated
varInfo.erase(src->varId());
}

auto isAssignment = [](const Token* varTok) -> const Token* {
if (varTok->varId()) {
const Token* top = varTok;
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23 changes: 23 additions & 0 deletions test/testleakautovar.cpp
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Expand Up @@ -64,6 +64,9 @@ class TestLeakAutoVar : public TestFixture {
TEST_CASE(assign25);
TEST_CASE(assign26);

TEST_CASE(memcpyWithPtr1); // #11542
TEST_CASE(memcpyWithPtr2);

TEST_CASE(isAutoDealloc);

TEST_CASE(realloc1);
Expand Down Expand Up @@ -631,6 +634,26 @@ class TestLeakAutoVar : public TestFixture {
ASSERT_EQUALS("", errout_str());
}

void memcpyWithPtr1() { // #11542
check("#include <string.h>\n"
"void f(char** old, char* value) {\n"
" char *str = strdup(value);\n"
" memcpy(old, &str, sizeof(char*));\n"
"}\n");
ASSERT_EQUALS("", errout_str());
}

void memcpyWithPtr2() {
check("#include <string.h>\n"
"void f(char* value) {\n"
" char *old = NULL;\n"
" char *str = strdup(value);\n"
" memcpy(&old, &str, sizeof(char*));\n"
"}\n");
// TODO: make this fail
ASSERT_EQUALS("", errout_str());
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Running cppcheck on this code on the command line (without any additional options) produces an error,but nothing happens in the test function.

What could the reason for this be?

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Maybe std.cfg is not loaded in that test, so strdup() and memcpy() are not recognized. There should be other tests where we load the library.

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@ludviggunne ludviggunne Sep 11, 2024 •
edited
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I'm just matching the token with "memcpy" though, is the library loading really required for that?

Edit: right, the strdup is crucial

}

void isAutoDealloc() {
check("void f() {\n"
" char *p = new char[100];"
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