The -Walloca-larger-than, -Wformat-length, and -Wformat-truncation
options do not mention LTO among the supported languages and so are
disabled when -flto is used, causing false negatives.
The attached patch adds the missing LTO to the three options. This
makes -Walloca-larger-than work with LTO but not the other two
options, implying that something else is preventing the gimple-ssa-
sprintf pass from running when -flto is enabled. I haven't had
the cycles to look into what that might be yet. Since the root
causes are independent I'd like to commit this patch first and
deal with the -Wformat-{length,truncation} problem separately,
under a new bug (or give someone with a better understanding of
LTO the opportunity to do it).
Thanks
Martin
PR c/78768 - -Walloca-larger-than and -Wformat-length warnings disabled by -flto
gcc/c-family/ChangeLog:
PR c/78768
* c.opt (-Walloca-larger-than, -Wformat-length, -Wformat-truncation):
Also enable for LTO.
gcc/testsuite/ChangeLog:
PR c/78768
* gcc.dg/pr78768.c: New test.
Index: gcc/c-family/c.opt
===================================================================
--- gcc/c-family/c.opt (revision 244294)
+++ gcc/c-family/c.opt (working copy)
@@ -313,7 +313,7 @@ C ObjC C++ ObjC++ Var(warn_alloc_zero) Warning
-Walloc-zero Warn for calls to allocation functions that specify zero bytes.
Walloca-larger-than=
-C ObjC C++ ObjC++ Var(warn_alloca_limit) Warning Joined RejectNegative UInteger
+C ObjC C++ LTO ObjC++ Var(warn_alloca_limit) Warning Joined RejectNegative UInteger
-Walloca-larger-than=<number> Warn on unbounded uses of
alloca, and on bounded uses of alloca whose bound can be larger than
<number> bytes.
@@ -521,7 +521,7 @@ C ObjC C++ ObjC++ Var(warn_format_extra_args) Warn
Warn if passing too many arguments to a function for its format string.
Wformat-length
-C ObjC C++ ObjC++ Warning Alias(Wformat-length=, 1, 0)
+C ObjC C++ LTO ObjC++ Warning Alias(Wformat-length=, 1, 0)
Warn about function calls with format strings that write past the end
of the destination region. Same as -Wformat-length=1.
@@ -538,7 +538,7 @@ C ObjC C++ ObjC++ Var(warn_format_signedness) Warn
Warn about sign differences with format functions.
Wformat-truncation
-C ObjC C++ ObjC++ Warning Alias(Wformat-truncation=, 1, 0)
+C ObjC C++ LTO ObjC++ Warning Alias(Wformat-truncation=, 1, 0)
Warn about calls to snprintf and similar functions that truncate output.
Same as -Wformat-truncation=1.
Index: gcc/testsuite/gcc.dg/pr78768.c
===================================================================
--- gcc/testsuite/gcc.dg/pr78768.c (revision 0)
+++ gcc/testsuite/gcc.dg/pr78768.c (working copy)
@@ -0,0 +1,13 @@
+/* PR c/78768 - -Walloca-larger-than and -Wformat-length warnings disabled
+ by -flto
+ { dg-do run }
+ { dg-options "-O2 -Walloca-larger-than=10 -Wformat -Wformat-length -flto" } */
+
+int main (void)
+{
+ char *d = (char *)__builtin_alloca (12); /* { dg-warning "argument to .alloca. is too large" } */
+
+ __builtin_sprintf (d, "%32s", "x"); /* { dg-warning "directive writing 32 bytes into a region of size 12" "-Wformat-length" { xfail *-*-* } } */
+
+ return 0;
+}
