Warn about the following:
char s[3] = "foo";
Initializing a char array with a string literal of the same length as
the size of the array is usually a mistake. Rarely is the case where
one wants to create a non-terminated character sequence from a string
literal.
In some cases, for writing faster code, one may want to use arrays
instead of pointers, since that removes the need for storing an array of
pointers apart from the strings themselves.
char *log_levels[] = { "info", "warning", "err" };
vs.
char log_levels[][7] = { "info", "warning", "err" };
This forces the programmer to specify a size, which might change if a
new entry is later added. Having no way to enforce null termination is
very dangerous, however, so it is useful to have a warning for this, so
that the compiler can make sure that the programmer didn't make any
mistakes. This warning catches the bug above, so that the programmer
will be able to fix it and write:
char log_levels[][8] = { "info", "warning", "err" };
This warning already existed as part of -Wc++-compat, but this patch
allows enabling it separately. It is also included in -Wextra, since
it may not always be desired (when unterminated character sequences are
wanted), but it's likely to be desired in most cases.
Since Wc++-compat now includes this warning, the test has to be modified
to expect the text of the new warning too, in .
Link:
Link:
Link:
Acked-by: Doug McIlroy
Cc: "G. Branden Robinson"
Cc: Ralph Corderoy
Cc: Dave Kemper
Cc: Larry McVoy
Cc: Andrew Pinski
Cc: Jonathan Wakely
Cc: Andrew Clayton
Cc: Martin Uecker
Cc: David Malcolm
Cc: Mike Stump
Cc: Joseph Myers
Cc: Sandra Loosemore
Signed-off-by: Alejandro Colomar
---
Range-diff against v6:
1: e8fd975bde7 ! 1: c0f3ffcca7a C, ObjC: Add
-Wunterminated-string-initialization
@@ gcc/doc/invoke.texi: arithmetic that may yield out of bounds values.
This warnin
+@opindex Wunterminated-string-initialization
+@opindex Wno-unterminated-string-initialization
-+@item -Wunterminated-string-initialization
++@item -Wunterminated-string-initialization @r{(C and Objective-C only)}
+Warn about character arrays
+initialized as unterminated character sequences
+with a string literal.
@@ gcc/doc/invoke.texi: arithmetic that may yield out of bounds values.
This warnin
+char arr[3] = "foo";
+@end smallexample
+
-+@option{-Wunterminated-string-initialization} is enabled by
@option{-Wextra}.
++This warning is enabled by @option{-Wextra} and @option{-Wc++-compat}.
++In C++, such initializations are an error.
+
@opindex Warray-compare
@opindex Wno-array-compare
gcc/c-family/c.opt| 4
gcc/c/c-typeck.cc | 6 +++---
gcc/doc/invoke.texi | 20 ++-
gcc/testsuite/gcc.dg/Wcxx-compat-14.c | 2 +-
.../Wunterminated-string-initialization.c | 6 ++
5 files changed, 33 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/Wunterminated-string-initialization.c
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 44b9c862c14..3837021747b 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1407,6 +1407,10 @@ Wunsuffixed-float-constants
C ObjC Var(warn_unsuffixed_float_constants) Warning
Warn about unsuffixed float constants.
+Wunterminated-string-initialization
+C ObjC Var(warn_unterminated_string_initialization) Warning LangEnabledBy(C
ObjC,Wextra || Wc++-compat)
+Warn about character arrays initialized as unterminated character sequences
with a string literal.
+
Wunused
C ObjC C++ ObjC++ LangEnabledBy(C ObjC C++ ObjC++,Wall)
; documented in common.opt
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index e55e887da14..7df9de819ed 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -8399,11 +8399,11 @@ digest_init (location_t init_loc, tree type, tree init,
tree origtype,
pedwarn_init (init_loc, 0,
("initializer-string for array of %qT "
"is too long"), typ1);
- else if (warn_cxx_compat
+ else if (warn_unterminated_string_initialization
&& compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
- warning_at (init_loc, OPT_Wc___compat,
+ warning_at (init_loc, OPT_Wunterminated_string_initialization,
("initializer-string for array of %qT "
-"is too long for C++"), typ1);
+"is too long"), typ1);
if (compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
{
unsigned HOST_WI
