[Sema] add -Walloca to flag uses of `alloca`

This CL adds an optional warning to diagnose uses of the
`__builtin_alloca` family of functions. The use of these functions is
discouraged by many, so it seems like a good idea to allow clang to warn
about it.

Patch by Elaina Guan!

Differential Revision: https://reviews.llvm.org/D64883

llvm-svn: 367067
This commit is contained in:
George Burgess IV 2019-07-25 22:23:40 +00:00
parent 29af3b4e67
commit 9d045a5c1e
3 changed files with 29 additions and 0 deletions

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@ -2779,6 +2779,11 @@ def err_no_accessor_for_property : Error<
def err_cannot_find_suitable_accessor : Error<
"cannot find suitable %select{getter|setter}0 for property %1">;
def warn_alloca : Warning<
"use of function %0 is discouraged; there is no way to check for failure but "
"failure may still occur, resulting in a possibly exploitable security vulnerability">,
InGroup<DiagGroup<"alloca">>, DefaultIgnore;
def warn_alloca_align_alignof : Warning<
"second argument to __builtin_alloca_with_align is supposed to be in bits">,
InGroup<DiagGroup<"alloca-with-align-alignof">>;

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@ -1179,6 +1179,10 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
case Builtin::BI__builtin_alloca_with_align:
if (SemaBuiltinAllocaWithAlign(TheCall))
return ExprError();
LLVM_FALLTHROUGH;
case Builtin::BI__builtin_alloca:
Diag(TheCall->getBeginLoc(), diag::warn_alloca)
<< TheCall->getDirectCallee();
break;
case Builtin::BI__assume:
case Builtin::BI__builtin_assume:

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@ -0,0 +1,20 @@
// RUN: %clang_cc1 -DSILENCE -fsyntax-only -verify -Wall %s
// RUN: %clang_cc1 -fsyntax-only -verify -Walloca %s
#ifdef SILENCE
// expected-no-diagnostics
#endif
void test1(int a) {
__builtin_alloca(a);
#ifndef SILENCE
// expected-warning@-2 {{use of function '__builtin_alloca' is discouraged; there is no way to check for failure but failure may still occur, resulting in a possibly exploitable security vulnerability}}
#endif
}
void test2(int a) {
__builtin_alloca_with_align(a, 32);
#ifndef SILENCE
// expected-warning@-2 {{use of function '__builtin_alloca_with_align' is discouraged; there is no way to check for failure but failure may still occur, resulting in a possibly exploitable security vulnerability}}
#endif
}