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[v2] c-format: Add -Wformat-int-precision option [PR80060]

Message ID 20211010231020.762020-1-daniil.stas@posteo.net
State New
Headers show
Series [v2] c-format: Add -Wformat-int-precision option [PR80060] | expand

Commit Message

Daniil Stas Oct. 10, 2021, 11:10 p.m. UTC
This option is enabled by default when -Wformat option is enabled. A
user can specify -Wno-format-int-precision to disable emitting
warnings when passing an argument of an incompatible integer type to
a 'd', 'i', 'o', 'u', 'x', or 'X' conversion specifier when it has
the same precision as the expected type.

Signed-off-by: Daniil Stas <daniil.stas@posteo.net>

gcc/c-family/ChangeLog:

	* c-format.c (check_format_types): Don't emit warnings when
	passing an argument of an incompatible integer type to
	a 'd', 'i', 'o', 'u', 'x', or 'X' conversion specifier when it has
	the same precision as the expected type if
	-Wno-format-int-precision option is specified.
	* c.opt: Add -Wformat-int-precision option.

gcc/ChangeLog:

	* doc/invoke.texi: Add -Wformat-int-precision option description.

gcc/testsuite/ChangeLog:

	* c-c++-common/Wformat-int-precision-1.c: New test.
	* c-c++-common/Wformat-int-precision-2.c: New test.
---
This is an update of patch "c-format: Add -Wformat-same-precision option [PR80060]".
The changes comparing to the first patch version:

- changed the option name to -Wformat-int-precision
- changed the option description as was suggested by Martin
- changed Wformat-int-precision-2.c to used dg-bogus instead of previous invalid
syntax

I also tried to combine the tests into one file with #pragma GCC diagnostic,
but looks like it's not possible. I want to test that when passing just -Wformat
option everything works as before my patch by default. And then in another test
case to check that passing -Wno-format-int-precision disables the warning. But
looks like in GCC you can't toggle the warnings such as
-Wno-format-int-precision individually but only can disable the general
-Wformat option that will disable all the formatting warnings together, which
is not the proper test.

 gcc/c-family/c-format.c                         |  2 +-
 gcc/c-family/c.opt                              |  6 ++++++
 gcc/doc/invoke.texi                             | 17 ++++++++++++++++-
 .../c-c++-common/Wformat-int-precision-1.c      |  7 +++++++
 .../c-c++-common/Wformat-int-precision-2.c      |  7 +++++++
 5 files changed, 37 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/Wformat-int-precision-1.c
 create mode 100644 gcc/testsuite/c-c++-common/Wformat-int-precision-2.c
diff mbox series

Patch

diff --git a/gcc/c-family/c-format.c b/gcc/c-family/c-format.c
index ca66c81f716..dd4436929f8 100644
--- a/gcc/c-family/c-format.c
+++ b/gcc/c-family/c-format.c
@@ -4243,7 +4243,7 @@  check_format_types (const substring_loc &fmt_loc,
 	  && (!pedantic || i < 2)
 	  && char_type_flag)
 	continue;
-      if (types->scalar_identity_flag
+      if ((types->scalar_identity_flag || !warn_format_int_precision)
 	  && (TREE_CODE (cur_type) == TREE_CODE (wanted_type)
 	      || (INTEGRAL_TYPE_P (cur_type)
 		  && INTEGRAL_TYPE_P (wanted_type)))
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 06457ac739e..f5b4af3f3f6 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -660,6 +660,12 @@  C ObjC C++ LTO ObjC++ Warning Alias(Wformat-overflow=, 1, 0) IntegerRange(0, 2)
 Warn about function calls with format strings that write past the end
 of the destination region.  Same as -Wformat-overflow=1.
 
+Wformat-int-precision
+C ObjC C++ ObjC++ Var(warn_format_int_precision) Warning LangEnabledBy(C ObjC C++ ObjC++,Wformat=,warn_format >= 1, 0)
+Warn when passing an argument of an incompatible integer type to a 'd', 'i',
+'o', 'u', 'x', or 'X' conversion specifier even when it has the same precision
+as the expected type.
+
 Wformat-security
 C ObjC C++ ObjC++ Var(warn_format_security) Warning LangEnabledBy(C ObjC C++ ObjC++,Wformat=, warn_format >= 2, 0)
 Warn about possible security problems with format functions.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 8b3ebcfbc4f..05dec6ba832 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -348,7 +348,7 @@  Objective-C and Objective-C++ Dialects}.
 -Werror  -Werror=*  -Wexpansion-to-defined  -Wfatal-errors @gol
 -Wfloat-conversion  -Wfloat-equal  -Wformat  -Wformat=2 @gol
 -Wno-format-contains-nul  -Wno-format-extra-args  @gol
--Wformat-nonliteral  -Wformat-overflow=@var{n} @gol
+-Wformat-nonliteral  -Wformat-overflow=@var{n} -Wformat-int-precision @gol
 -Wformat-security  -Wformat-signedness  -Wformat-truncation=@var{n} @gol
 -Wformat-y2k  -Wframe-address @gol
 -Wframe-larger-than=@var{byte-size}  -Wno-free-nonheap-object @gol
@@ -6056,6 +6056,21 @@  If @option{-Wformat} is specified, also warn if the format string is not a
 string literal and so cannot be checked, unless the format function
 takes its format arguments as a @code{va_list}.
 
+@item -Wformat-int-precision
+@opindex Wformat-int-precision
+@opindex Wno-format-int-precision
+Warn when passing an argument of an incompatible integer type to
+a @samp{d}, @samp{i}, @samp{o}, @samp{u}, @samp{x}, or @samp{X} conversion
+specifier even when it has the same precision as the expected type.
+For example, on targets where int64_t is a typedef for long, the warning
+is issued for the printf call below even when both long and long long have
+the same size and precision.
+
+@smallexample
+  extern int64_t n;
+  printf ("%lli", n);
+@end smallexample
+
 @item -Wformat-security
 @opindex Wformat-security
 @opindex Wno-format-security
diff --git a/gcc/testsuite/c-c++-common/Wformat-int-precision-1.c b/gcc/testsuite/c-c++-common/Wformat-int-precision-1.c
new file mode 100644
index 00000000000..fbc11e4200a
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wformat-int-precision-1.c
@@ -0,0 +1,7 @@ 
+/* { dg-do compile { target lp64 } } */
+/* { dg-options "-Wformat" } */
+
+void test ()
+{
+  __builtin_printf ("%lu\n", (long long) 1); /* { dg-warning "expects argument of type" } */
+}
diff --git a/gcc/testsuite/c-c++-common/Wformat-int-precision-2.c b/gcc/testsuite/c-c++-common/Wformat-int-precision-2.c
new file mode 100644
index 00000000000..63536bf5ff2
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wformat-int-precision-2.c
@@ -0,0 +1,7 @@ 
+/* { dg-do compile { target lp64 } } */
+/* { dg-options "-Wformat -Wno-format-int-precision" } */
+
+void test ()
+{
+  __builtin_printf ("%lu\n", (long long) 1); /* { dg-bogus "expects argument of type" } */
+}