Message ID | 20220325212643.773729-1-dmalcolm@redhat.com |
---|---|
State | New |
Headers | show |
Series | gimple-fold: fix location of loads for memory ops [PR104308] | expand |
On Fri, Mar 25, 2022 at 10:27 PM David Malcolm via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > PR analyzer/104308 reports that when -Wanalyzer-use-of-uninitialized-value > complains about certain memmove operations where the source is > uninitialized, the diagnostic uses UNKNOWN_LOCATION: > > In function 'main': > cc1: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value] > 'main': event 1 > | > |pr104308.c:5:8: > | 5 | char s[5]; /* { dg-message "region created on stack here" } */ > | | ^ > | | | > | | (1) region created on stack here > | > 'main': event 2 > | > |cc1: > | (2): use of uninitialized value '*(short unsigned int *)&s + 1' here > | > > The issue is that gimple_fold_builtin_memory_op converts a memmove to: > > _3 = MEM <unsigned short> [(char * {ref-all})_1]; > MEM <unsigned short> [(char * {ref-all})&s] = _3; > > but only sets the location of the 2nd stmt, not the 1st. > > Fixed thusly, giving: > > pr104308.c: In function 'main': > pr104308.c:6:3: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value] > 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */ > | ^~~~~~~~~~~~~~~~~~~~ > 'main': events 1-2 > | > | 5 | char s[5]; /* { dg-message "region created on stack here" } */ > | | ^ > | | | > | | (1) region created on stack here > | 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */ > | | ~~~~~~~~~~~~~~~~~~~~ > | | | > | | (2) use of uninitialized value '*(short unsigned int *)&s + 1' here > | > > One side-effect of this change is a change in part of the output of > gcc.dg/uninit-40.c from: > > uninit-40.c:47:3: warning: ‘*(long unsigned int *)(&u[1][0][0])’ is used uninitialized [-Wuninitialized] > 47 | __builtin_memcpy (&v[1], &u[1], sizeof (V)); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > uninit-40.c:45:5: note: ‘*(long unsigned int *)(&u[1][0][0])’ was declared here > 45 | V u[2], v[2]; > | ^ > > to: > > uninit-40.c:47:3: warning: ‘u’ is used uninitialized [-Wuninitialized] > 47 | __builtin_memcpy (&v[1], &u[1], sizeof (V)); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > uninit-40.c:45:5: note: ‘u’ declared here > 45 | V u[2], v[2]; > | ^ > > What's happening is that pass "early_uninit"(29)'s call to > maybe_warn_operand is guarded by this condition: > 1051 else if (gimple_assign_load_p (stmt) > 1052 && gimple_has_location (stmt)) > > Before the patch, the stmt: > _3 = MEM <unsigned long> [(char * {ref-all})&u + 8B]; > has no location, and so early_uninit skips this operand at line > 1052 above. Later, pass "uninit"(217) tests the var_decl "u$8", and > emits a warning for it. > > With the patch, the stmt has a location, and so early_uninit emits a > warning for "u" and sets a NW_UNINIT warning suppression at that > location. Later, pass "uninit"(217)'s test of "u$8" is rejected > due to that per-location suppression of uninit warnings, from the > earlier warning. > > Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu. > > OK for stage 4? or for next stage 1? OK for stage4. Thanks, Richard. > gcc/ChangeLog: > PR analyzer/104308 > * gimple-fold.cc (gimple_fold_builtin_memory_op): When optimizing > to loads then stores, set the location of the new load stmt. > > gcc/testsuite/ChangeLog: > PR analyzer/104308 > * gcc.dg/analyzer/pr104308.c: New test. > * gcc.dg/uninit-40.c (foo): Update expression in expected message. > > Signed-off-by: David Malcolm <dmalcolm@redhat.com> > --- > gcc/gimple-fold.cc | 1 + > gcc/testsuite/gcc.dg/analyzer/pr104308.c | 8 ++++++++ > gcc/testsuite/gcc.dg/uninit-40.c | 2 +- > 3 files changed, 10 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/gcc.dg/analyzer/pr104308.c > > diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc > index 5eff7d68ac1..e73bc6a7137 100644 > --- a/gcc/gimple-fold.cc > +++ b/gcc/gimple-fold.cc > @@ -1039,6 +1039,7 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi, > new_stmt); > gimple_assign_set_lhs (new_stmt, srcmem); > gimple_set_vuse (new_stmt, gimple_vuse (stmt)); > + gimple_set_location (new_stmt, loc); > gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT); > } > if (dest_align < GET_MODE_ALIGNMENT (mode)) > diff --git a/gcc/testsuite/gcc.dg/analyzer/pr104308.c b/gcc/testsuite/gcc.dg/analyzer/pr104308.c > new file mode 100644 > index 00000000000..9cd5ee6feee > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/analyzer/pr104308.c > @@ -0,0 +1,8 @@ > +#include <string.h> > + > +int main() > +{ > + char s[5]; /* { dg-message "region created on stack here" } */ > + memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */ > + return 0; > +} > diff --git a/gcc/testsuite/gcc.dg/uninit-40.c b/gcc/testsuite/gcc.dg/uninit-40.c > index 8708079d397..567707a885e 100644 > --- a/gcc/testsuite/gcc.dg/uninit-40.c > +++ b/gcc/testsuite/gcc.dg/uninit-40.c > @@ -44,7 +44,7 @@ foo (int *q) > /* memcpy folding is too target dependent to test it everywhere. */ > V u[2], v[2]; > u[0][0][0] = 1; > - __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'\\*\\(\(long \)?long unsigned int \\*\\)\\(&u\\\[1\\\]\\\[0\\\]\\\[0\\\]\\)' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */ > + __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'u' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */ > baz (&v[1]); > #endif > } > -- > 2.26.3 >
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc index 5eff7d68ac1..e73bc6a7137 100644 --- a/gcc/gimple-fold.cc +++ b/gcc/gimple-fold.cc @@ -1039,6 +1039,7 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi, new_stmt); gimple_assign_set_lhs (new_stmt, srcmem); gimple_set_vuse (new_stmt, gimple_vuse (stmt)); + gimple_set_location (new_stmt, loc); gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT); } if (dest_align < GET_MODE_ALIGNMENT (mode)) diff --git a/gcc/testsuite/gcc.dg/analyzer/pr104308.c b/gcc/testsuite/gcc.dg/analyzer/pr104308.c new file mode 100644 index 00000000000..9cd5ee6feee --- /dev/null +++ b/gcc/testsuite/gcc.dg/analyzer/pr104308.c @@ -0,0 +1,8 @@ +#include <string.h> + +int main() +{ + char s[5]; /* { dg-message "region created on stack here" } */ + memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */ + return 0; +} diff --git a/gcc/testsuite/gcc.dg/uninit-40.c b/gcc/testsuite/gcc.dg/uninit-40.c index 8708079d397..567707a885e 100644 --- a/gcc/testsuite/gcc.dg/uninit-40.c +++ b/gcc/testsuite/gcc.dg/uninit-40.c @@ -44,7 +44,7 @@ foo (int *q) /* memcpy folding is too target dependent to test it everywhere. */ V u[2], v[2]; u[0][0][0] = 1; - __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'\\*\\(\(long \)?long unsigned int \\*\\)\\(&u\\\[1\\\]\\\[0\\\]\\\[0\\\]\\)' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */ + __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'u' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */ baz (&v[1]); #endif }
PR analyzer/104308 reports that when -Wanalyzer-use-of-uninitialized-value complains about certain memmove operations where the source is uninitialized, the diagnostic uses UNKNOWN_LOCATION: In function 'main': cc1: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value] 'main': event 1 | |pr104308.c:5:8: | 5 | char s[5]; /* { dg-message "region created on stack here" } */ | | ^ | | | | | (1) region created on stack here | 'main': event 2 | |cc1: | (2): use of uninitialized value '*(short unsigned int *)&s + 1' here | The issue is that gimple_fold_builtin_memory_op converts a memmove to: _3 = MEM <unsigned short> [(char * {ref-all})_1]; MEM <unsigned short> [(char * {ref-all})&s] = _3; but only sets the location of the 2nd stmt, not the 1st. Fixed thusly, giving: pr104308.c: In function 'main': pr104308.c:6:3: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value] 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */ | ^~~~~~~~~~~~~~~~~~~~ 'main': events 1-2 | | 5 | char s[5]; /* { dg-message "region created on stack here" } */ | | ^ | | | | | (1) region created on stack here | 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */ | | ~~~~~~~~~~~~~~~~~~~~ | | | | | (2) use of uninitialized value '*(short unsigned int *)&s + 1' here | One side-effect of this change is a change in part of the output of gcc.dg/uninit-40.c from: uninit-40.c:47:3: warning: ‘*(long unsigned int *)(&u[1][0][0])’ is used uninitialized [-Wuninitialized] 47 | __builtin_memcpy (&v[1], &u[1], sizeof (V)); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ uninit-40.c:45:5: note: ‘*(long unsigned int *)(&u[1][0][0])’ was declared here 45 | V u[2], v[2]; | ^ to: uninit-40.c:47:3: warning: ‘u’ is used uninitialized [-Wuninitialized] 47 | __builtin_memcpy (&v[1], &u[1], sizeof (V)); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ uninit-40.c:45:5: note: ‘u’ declared here 45 | V u[2], v[2]; | ^ What's happening is that pass "early_uninit"(29)'s call to maybe_warn_operand is guarded by this condition: 1051 else if (gimple_assign_load_p (stmt) 1052 && gimple_has_location (stmt)) Before the patch, the stmt: _3 = MEM <unsigned long> [(char * {ref-all})&u + 8B]; has no location, and so early_uninit skips this operand at line 1052 above. Later, pass "uninit"(217) tests the var_decl "u$8", and emits a warning for it. With the patch, the stmt has a location, and so early_uninit emits a warning for "u" and sets a NW_UNINIT warning suppression at that location. Later, pass "uninit"(217)'s test of "u$8" is rejected due to that per-location suppression of uninit warnings, from the earlier warning. Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu. OK for stage 4? or for next stage 1? gcc/ChangeLog: PR analyzer/104308 * gimple-fold.cc (gimple_fold_builtin_memory_op): When optimizing to loads then stores, set the location of the new load stmt. gcc/testsuite/ChangeLog: PR analyzer/104308 * gcc.dg/analyzer/pr104308.c: New test. * gcc.dg/uninit-40.c (foo): Update expression in expected message. Signed-off-by: David Malcolm <dmalcolm@redhat.com> --- gcc/gimple-fold.cc | 1 + gcc/testsuite/gcc.dg/analyzer/pr104308.c | 8 ++++++++ gcc/testsuite/gcc.dg/uninit-40.c | 2 +- 3 files changed, 10 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.dg/analyzer/pr104308.c