On 11/1/2017 1:02 PM, Jason Merrill wrote:
On Tue, Oct 31, 2017 at 12:17 PM, Mukesh Kapoor
<mukesh.kap...@oracle.com> wrote:
On 10/25/2017 6:44 PM, Mukesh Kapoor wrote:
On 10/25/2017 4:20 AM, Nathan Sidwell wrote:
On 10/25/2017 12:03 AM, Mukesh Kapoor wrote:
Thanks for pointing this out. Checking in the front end will be
difficult because the front end gets tokens after macro expansion. I think
the difficulty of fixing this bug comes because of the requirement to
maintain backward compatibility with the option -Wliteral-suffix for
-std=c++11.
IIUC the warning's intent is to catch cases of:
printf ("some format"PRIx64 ..., ...);
where there's no space between the string literals and the PRIx64 macro.
I suspect it's very common for there to be a following string-literal, so
perhaps the preprocessor could detect:
<string-literal>NON-FN-MACRO<maybe-space><string-literal>
and warn on that sequence?
Yes, this can be done easily and this is also the usage mentioned in the
man page. I made this change in the compiler, bootstrapped it and ran the
tests. The following two tests fail after the fix:
g++.dg/cpp0x/Wliteral-suffix.C
g++.dg/cpp0x/warn_cxx0x4.C
Both tests have code similar to the following (from Wliteral-suffix.C):
#define BAR "bar"
#define PLUS_ONE + 1
char c = '3'PLUS_ONE; // { dg-warning "invalid suffix on literal" }
char s[] = "foo"BAR; // { dg-warning "invalid suffix on literal" }
Other compilers don't accept this code. Maybe I should just modify these
tests to have error messages instead of warnings and submit my revised fix?
Actually, according to the man page for -Wliteral-suffix, only macro names
that don't start with an underscore should be considered when issuing a
warning:
-Wliteral-suffix (C++ and Objective-C++ only)
Warn when a string or character literal is followed by a
ud-suffix
which does not begin with an underscore...
So the fix is simply to check if the macro name in is_macro() starts with an
underscore. The function is_macro() is called only at three places. At two
places it's used to check for the warning related to -Wliteral-suffix and
the check for underscore should be made for these two cases; at one place it
is used to check for the warning related to -Wc++11-compat and there is no
need to check for underscore for this case.
The fix is simply to pass a bool flag as an additional argument to
is_macro() to decide whether the macro name starts with an underscore or
not. I have tested the attached patch on x86_64-linux. Thanks.
Rather than add a mysterious parameter to is_macro, how about checking
*cur != '_' before we call it?
This is a good suggestion. I have attached the revised patch. Thanks.
Mukesh
/libcpp
2017-10-31 Mukesh Kapoor <mukesh.kap...@oracle.com>
PR c++/80955
* lex.c (lex_string): When checking for a valid macro for the
warning related to -Wliteral-suffix (CPP_W_LITERAL_SUFFIX),
check that the macro name does not start with an underscore
before calling is_macro().
/testsuite
2017-10-31 Mukesh Kapoor <mukesh.kap...@oracle.com>
PR c++/80955
* g++.dg/cpp0x/udlit-macros.C: New.
Index: gcc/testsuite/g++.dg/cpp0x/udlit-macros.C
===================================================================
--- gcc/testsuite/g++.dg/cpp0x/udlit-macros.C (revision 0)
+++ gcc/testsuite/g++.dg/cpp0x/udlit-macros.C (working copy)
@@ -0,0 +1,31 @@
+// PR c++/80955
+// { dg-do compile { target c++11 } }
+
+#define __STDC_FORMAT_MACROS
+#include <inttypes.h>
+#include <stdio.h>
+#include <string.h>
+
+using size_t = decltype(sizeof(0));
+#define _zero
+#define _ID _xx
+int operator""_zero(const char*, size_t) { return 0; }
+int operator""_ID(const char*, size_t) { return 0; }
+
+int main()
+{
+ int64_t i64 = 123;
+ char buf[100];
+ sprintf(buf, "%"PRId64"abc", i64); // { dg-warning "invalid suffix on
literal" }
+ return strcmp(buf, "123abc")
+ + ""_zero
+ + "bob"_zero
+ + R"#(raw
+ string)#"_zero
+ + "xx"_ID
+ + ""_ID
+ + R"AA(another
+ raw
+ string)AA"_ID;
+}
+
Index: libcpp/lex.c
===================================================================
--- libcpp/lex.c (revision 254048)
+++ libcpp/lex.c (working copy)
@@ -1871,8 +1871,9 @@
/* If a string format macro, say from inttypes.h, is placed touching
a string literal it could be parsed as a C++11 user-defined string
literal thus breaking the program.
- Try to identify macros with is_macro. A warning is issued. */
- if (is_macro (pfile, cur))
+ Try to identify macros with is_macro. A warning is issued.
+ The macro name should not start with '_' for this warning. */
+ if ((*cur != '_') && is_macro (pfile, cur))
{
/* Raise a warning, but do not consume subsequent tokens. */
if (CPP_OPTION (pfile, warn_literal_suffix) && !pfile->state.skipping)
@@ -2001,8 +2002,9 @@
/* If a string format macro, say from inttypes.h, is placed touching
a string literal it could be parsed as a C++11 user-defined string
literal thus breaking the program.
- Try to identify macros with is_macro. A warning is issued. */
- if (is_macro (pfile, cur))
+ Try to identify macros with is_macro. A warning is issued.
+ The macro name should not start with '_' for this warning. */
+ if ((*cur != '_') && is_macro (pfile, cur))
{
/* Raise a warning, but do not consume subsequent tokens. */
if (CPP_OPTION (pfile, warn_literal_suffix) && !pfile->state.skipping)
