The attached patch eliminates -Wstringop-truncation false
positives reported in bug 84480 - bogus -Wstringop-truncation
despite assignment with an inlined string literal. It does
that by delegating early strncpy checks during folding to
the same machinery in tree-ssa-strlen that looks for a NUL
assignment to the destination the next statement.
The patch also adds inlining context to the warnings via
the %G directive.
Tested on x86_64-linux with no regressions.
Martin
PR tree-optimization/84480 - bogus -Wstringop-truncation despite assignment with an inlined string literal
gcc/ChangeLog:
PR tree-optimization/84480
* gimple-fold.c (gimple_fold_builtin_strcpy): Move warnings
to maybe_diag_stxncpy_trunc. Call it.
* tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Integrate warnings
from gimple_fold_builtin_strcpy. Print inlining stack.
(handle_builtin_stxncpy): Print inlining stack.
* tree-ssa-strlen.h (maybe_diag_stxncpy_trunc): Declare.
gcc/testsuite/ChangeLog:
PR tree-optimization/84480
* c-c++-common/Wstringop-truncation.c: Adjust text of expected warnings.
* g++.dg/warn/Wstringop-truncation-1.C: New test.
Index: gcc/gimple-fold.c
===
--- gcc/gimple-fold.c (revision 257875)
+++ gcc/gimple-fold.c (working copy)
@@ -65,6 +65,7 @@ along with GCC; see the file COPYING3. If not see
#include "intl.h"
#include "calls.h"
#include "tree-vector-builder.h"
+#include "tree-ssa-strlen.h"
/* Return true when DECL can be referenced from current unit.
FROM_DECL (if non-null) specify constructor of variable DECL was taken from.
@@ -1710,38 +1711,9 @@ gimple_fold_builtin_strncpy (gimple_stmt_iterator
if (tree_int_cst_lt (ssize, len))
return false;
- if (!nonstring)
-{
- if (tree_int_cst_lt (len, slen))
- {
- tree fndecl = gimple_call_fndecl (stmt);
- gcall *call = as_a (stmt);
+ /* Diagnose truncation that leaves the copy unterminated. */
+ maybe_diag_stxncpy_trunc (*gsi, src, len);
- warning_at (loc, OPT_Wstringop_truncation,
- (tree_int_cst_equal (size_one_node, len)
- ? G_("%G%qD output truncated copying %E byte "
- "from a string of length %E")
- : G_("%G%qD output truncated copying %E bytes "
- "from a string of length %E")),
- call, fndecl, len, slen);
- }
- else if (tree_int_cst_equal (len, slen))
- {
- tree fndecl = gimple_call_fndecl (stmt);
- gcall *call = as_a (stmt);
-
- warning_at (loc, OPT_Wstringop_truncation,
- (tree_int_cst_equal (size_one_node, len)
- ? G_("%G%qD output truncated before terminating nul "
- "copying %E byte from a string of the same "
- "length")
- : G_("%G%qD output truncated before terminating nul "
- "copying %E bytes from a string of the same "
- "length")),
- call, fndecl, len);
- }
-}
-
/* OK transform into builtin memcpy. */
tree fn = builtin_decl_implicit (BUILT_IN_MEMCPY);
if (!fn)
Index: gcc/testsuite/c-c++-common/Wstringop-truncation.c
===
--- gcc/testsuite/c-c++-common/Wstringop-truncation.c (revision 257875)
+++ gcc/testsuite/c-c++-common/Wstringop-truncation.c (working copy)
@@ -188,7 +188,7 @@ void test_strncpy_ptr (char *d, const char* s, con
CPY (d, CHOOSE (s, t), 2);
CPY (d, CHOOSE ("", "123"), 1); /* { dg-warning ".strncpy\[^\n\r\]* output may be truncated copying 1 byte from a string of length 3" } */
- CPY (d, CHOOSE ("1", "123"), 1); /* { dg-warning ".strncpy\[^\n\r\]* output truncated copying 1 byte from a string of length 1" } */
+ CPY (d, CHOOSE ("1", "123"), 1); /* { dg-warning ".strncpy\[^\n\r\]* output truncated before terminating nul copying 1 byte from a string of the same length" } */
CPY (d, CHOOSE ("12", "123"), 1); /* { dg-warning ".strncpy\[^\n\r\]* output truncated copying 1 byte from a string of length 2" } */
CPY (d, CHOOSE ("123", "12"), 1); /* { dg-warning ".strncpy\[^\n\r\]* output truncated copying 1 byte from a string of length 2" } */
@@ -331,7 +331,7 @@ void test_strncpy_array (Dest *pd, int i, const ch
/* This might be better written using memcpy() but it's safe so
it probably shouldn't be diagnosed. It currently triggers
a warning because of bug 81704. */
-strncpy (dst7, "0123456", sizeof dst7); /* { dg-bogus "truncated" "bug 81704" { xfail *-*-* } } */
+strncpy (dst7, "0123456", sizeof dst7); /* { dg-bogus "\\\[-Wstringop-truncation]" "bug 81704" { xfail *-*-* } } */
dst7[sizeof dst7 - 1] = '\0';
sink (dst7);
}
@@ -350,7 +350,7 @@ void test_strncpy_array (Dest *pd, int i, const ch
}
{
-strncpy (pd->a5, "01234", sizeof pd->a5); /* { dg-bogus "truncated" "bug 81704" { xfail *-*-* } } */
+strncpy (pd->a5, "01234", sizeof pd->a5); /* { dg-bogus "\\\[-Wstringop-truncation]" "bug 81704" { xfail *-*-* } } */
pd->a5[sizeof pd->a5 - 1] = '\0';
sink
