glider created this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Initially concerns have been raised that -ftrivial-auto-var-init=zero
potentially defines a new dialect of C++, therefore this option was
guarded with
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang.
The guard flag name suggests that at some point
-ftrivial-auto-var-init=pattern will perform on par with
-ftrivial-auto-var-init=zero, thus making it possible to remove the
latter from Clang.
However this isn't going to happen in the nearest future, at least not
on X86, where `memset(object, 0, size)` is still lowered to a more
efficient code than `memset(object, 0xAA, size)`.
Therefore security-minded people may still need an easy way to
zero-initialize all the locals to keep the performance penalty low.
For Linux kernel, which already uses a non-standard dialect of C,
introducing yet another hardening feature doesn't radically change the
situation. Other C codebases also tend to use non-standard features more
often, so the mentioned guard flag only complicates the adoption of
auto-initialization for them, not actually protecting their purity.
As a compromise solution, let
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
remain mandatory for -ftrivial-auto-var-init=zero in C++ mode and make
it optional in the C mode.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D64742
Files:
clang/lib/Driver/ToolChains/Clang.cpp
clang/test/Driver/clang_f_opts.c
Index: clang/test/Driver/clang_f_opts.c
===================================================================
--- clang/test/Driver/clang_f_opts.c
+++ clang/test/Driver/clang_f_opts.c
@@ -566,7 +566,10 @@
// RUN: %clang -### -S -ftrivial-auto-var-init=uninitialized %s 2>&1 |
FileCheck -check-prefix=CHECK-TRIVIAL-UNINIT %s
// RUN: %clang -### -S -ftrivial-auto-var-init=pattern %s 2>&1 | FileCheck
-check-prefix=CHECK-TRIVIAL-PATTERN %s
// RUN: %clang -### -S -ftrivial-auto-var-init=zero
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang %s
2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-GOOD %s
-// RUN: %clang -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck
-check-prefix=CHECK-TRIVIAL-ZERO-BAD %s
+// RUN: %clang -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck
-check-prefix=CHECK-TRIVIAL-ZERO-GOOD %s
+// RUN: %clangxx -### -S -ftrivial-auto-var-init=zero
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang %s
2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-GOOD %s
+// RUN: %clangxx -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck
-check-prefix=CHECK-TRIVIAL-ZERO-BAD %s
+
// CHECK-TRIVIAL-UNINIT-NOT: hasn't been enabled
// CHECK-TRIVIAL-PATTERN-NOT: hasn't been enabled
// CHECK-TRIVIAL-ZERO-GOOD-NOT: hasn't been enabled
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -2544,7 +2544,8 @@
static void RenderTrivialAutoVarInitOptions(const Driver &D,
const ToolChain &TC,
const ArgList &Args,
- ArgStringList &CmdArgs) {
+ ArgStringList &CmdArgs,
+ const InputInfo &Input) {
auto DefaultTrivialAutoVarInit = TC.GetDefaultTrivialAutoVarInit();
StringRef TrivialAutoVarInit = "";
@@ -2578,7 +2579,9 @@
}
if (!TrivialAutoVarInit.empty()) {
- if (TrivialAutoVarInit == "zero" &&
!Args.hasArg(options::OPT_enable_trivial_var_init_zero))
+ if (TrivialAutoVarInit == "zero" &&
+ !Args.hasArg(options::OPT_enable_trivial_var_init_zero) &&
+ (Input.getType() != types::TY_C))
D.Diag(diag::err_drv_trivial_auto_var_init_zero_disabled);
CmdArgs.push_back(
Args.MakeArgString("-ftrivial-auto-var-init=" + TrivialAutoVarInit));
@@ -4623,7 +4626,7 @@
CmdArgs.push_back(Args.MakeArgString("-mspeculative-load-hardening"));
RenderSSPOptions(TC, Args, CmdArgs, KernelOrKext);
- RenderTrivialAutoVarInitOptions(D, TC, Args, CmdArgs);
+ RenderTrivialAutoVarInitOptions(D, TC, Args, CmdArgs, Input);
// Translate -mstackrealign
if (Args.hasFlag(options::OPT_mstackrealign, options::OPT_mno_stackrealign,
Index: clang/test/Driver/clang_f_opts.c
===================================================================
--- clang/test/Driver/clang_f_opts.c
+++ clang/test/Driver/clang_f_opts.c
@@ -566,7 +566,10 @@
// RUN: %clang -### -S -ftrivial-auto-var-init=uninitialized %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-UNINIT %s
// RUN: %clang -### -S -ftrivial-auto-var-init=pattern %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-PATTERN %s
// RUN: %clang -### -S -ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-GOOD %s
-// RUN: %clang -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-BAD %s
+// RUN: %clang -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-GOOD %s
+// RUN: %clangxx -### -S -ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-GOOD %s
+// RUN: %clangxx -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-BAD %s
+
// CHECK-TRIVIAL-UNINIT-NOT: hasn't been enabled
// CHECK-TRIVIAL-PATTERN-NOT: hasn't been enabled
// CHECK-TRIVIAL-ZERO-GOOD-NOT: hasn't been enabled
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -2544,7 +2544,8 @@
static void RenderTrivialAutoVarInitOptions(const Driver &D,
const ToolChain &TC,
const ArgList &Args,
- ArgStringList &CmdArgs) {
+ ArgStringList &CmdArgs,
+ const InputInfo &Input) {
auto DefaultTrivialAutoVarInit = TC.GetDefaultTrivialAutoVarInit();
StringRef TrivialAutoVarInit = "";
@@ -2578,7 +2579,9 @@
}
if (!TrivialAutoVarInit.empty()) {
- if (TrivialAutoVarInit == "zero" && !Args.hasArg(options::OPT_enable_trivial_var_init_zero))
+ if (TrivialAutoVarInit == "zero" &&
+ !Args.hasArg(options::OPT_enable_trivial_var_init_zero) &&
+ (Input.getType() != types::TY_C))
D.Diag(diag::err_drv_trivial_auto_var_init_zero_disabled);
CmdArgs.push_back(
Args.MakeArgString("-ftrivial-auto-var-init=" + TrivialAutoVarInit));
@@ -4623,7 +4626,7 @@
CmdArgs.push_back(Args.MakeArgString("-mspeculative-load-hardening"));
RenderSSPOptions(TC, Args, CmdArgs, KernelOrKext);
- RenderTrivialAutoVarInitOptions(D, TC, Args, CmdArgs);
+ RenderTrivialAutoVarInitOptions(D, TC, Args, CmdArgs, Input);
// Translate -mstackrealign
if (Args.hasFlag(options::OPT_mstackrealign, options::OPT_mno_stackrealign,
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
