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varasm: Two SECTION_RETAIN fixes [PR100130]

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switch_to_section warns if we try to output a retain decl in a
section without a retain flag, or if we try to output a non-retain
decl in a section with a retain flag.  However, the warning only
applied if we were trying to “switch” to the current section.
This works if all decls that use a section are generated consecutively,
but not if there is an unrelated decl in between.

This patch makes the check unconditional, but suppresses the warning
if we're writing the section's named.decl (i.e. the decl from which
the section name and original flags were derived).

Also, the warning didn't fire for -fsection-anchors, for two reasons:
we allowed retain and non-retain decls to be put into the same block,
and we didn't pass a decl to switch_to_section.

Although these are arguably separate bugs, it isn't easy to fix them
independently without temporarily regressing -fsection-anchor targets.

gcc/
	PR middle-end/100130
	* varasm.c (get_block_for_decl): Make sure that any use of the
	retain attribute matches the section's retain flag.
	(switch_to_section): Check for retain mismatches even when
	changing sections, but do not warn if the given decl is the
	section's named.decl.
	(output_object_block): Pass the first decl in the block (if any)
	to switch_to_section.

gcc/testsuite/
	PR middle-end/100130
	* c-c++-common/attr-retain-10.c: New test.
	* c-c++-common/attr-retain-11.c: Likewise.
This commit is contained in:
Richard Sandiford 2021-04-21 09:08:44 +01:00
parent cb60e56d4a
commit b67778b599
3 changed files with 54 additions and 28 deletions
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11
gcc/testsuite/c-c++-common/attr-retain-10.c Normal file
View file

@ -0,0 +1,11 @@
/* { dg-do compile { target R_flag_in_section } } */
/* { dg-skip-if "non-ELF target" { *-*-darwin* powerpc*-*-aix* } } */
/* { dg-options "-Wall -O2 -fno-toplevel-reorder" } */
int __attribute__((used,retain,section(".data.foo"))) foo2 = 2;
int between = 1;
int __attribute__((section(".data.foo"))) foo1 = 1;
/* { dg-warning "'.*' without 'retain' attribute and '.*' with 'retain' attribute are placed in a section with the same name" "" { target R_flag_in_section } .-1 } */
/* { dg-final { scan-assembler ".data.foo,\"aw\"" { target R_flag_in_section } } } */
/* { dg-final { scan-assembler ".data.foo,\"awR\"" { target R_flag_in_section } } } */

11
gcc/testsuite/c-c++-common/attr-retain-11.c Normal file
View file

@ -0,0 +1,11 @@
/* { dg-do compile { target R_flag_in_section } } */
/* { dg-skip-if "non-ELF target" { *-*-darwin* powerpc*-*-aix* } } */
/* { dg-options "-Wall -O2 -fno-toplevel-reorder" } */
int __attribute__((section(".data.foo"))) foo1 = 1;
/* { dg-warning "'.*' without 'retain' attribute and '.*' with 'retain' attribute are placed in a section with the same name" "" { target R_flag_in_section } .-1 } */
int between = 1;
int __attribute__((used,retain,section(".data.foo"))) foo2 = 2;
/* { dg-final { scan-assembler ".data.foo,\"aw\"" { target R_flag_in_section } } } */
/* { dg-final { scan-assembler ".data.foo,\"awR\"" { target R_flag_in_section } } } */

60
gcc/varasm.c
View file

@ -1314,6 +1314,10 @@ get_block_for_decl (tree decl)
if (SECTION_STYLE (sect) == SECTION_NOSWITCH)
return NULL;
if (bool (lookup_attribute ("retain", DECL_ATTRIBUTES (decl)))
!= bool (sect->common.flags & SECTION_RETAIN))
return NULL;
return get_block_for_section (sect);
}
@ -7758,33 +7762,33 @@ output_section_asm_op (const void *directive)
void
switch_to_section (section *new_section, tree decl)
{
if (in_section == new_section)
bool retain_p;
if ((new_section->common.flags & SECTION_NAMED)
&& decl != nullptr
&& DECL_P (decl)
&& ((retain_p = !!lookup_attribute ("retain",
DECL_ATTRIBUTES (decl)))
!= !!(new_section->common.flags & SECTION_RETAIN)))
{
bool retain_p;
if ((new_section->common.flags & SECTION_NAMED)
&& decl != nullptr
&& DECL_P (decl)
&& ((retain_p = !!lookup_attribute ("retain",
DECL_ATTRIBUTES (decl)))
!= !!(new_section->common.flags & SECTION_RETAIN)))
{
/* If the SECTION_RETAIN bit doesn't match, switch to a new
section. */
tree used_decl, no_used_decl;
/* If the SECTION_RETAIN bit doesn't match, switch to a new
section. */
tree used_decl, no_used_decl;
if (retain_p)
{
new_section->common.flags |= SECTION_RETAIN;
used_decl = decl;
no_used_decl = new_section->named.decl;
}
else
{
new_section->common.flags &= ~(SECTION_RETAIN
| SECTION_DECLARED);
used_decl = new_section->named.decl;
no_used_decl = decl;
}
if (retain_p)
{
new_section->common.flags |= SECTION_RETAIN;
used_decl = decl;
no_used_decl = new_section->named.decl;
}
else
{
new_section->common.flags &= ~(SECTION_RETAIN
| SECTION_DECLARED);
used_decl = new_section->named.decl;
no_used_decl = decl;
}
if (no_used_decl != used_decl)
{
warning (OPT_Wattributes,
"%+qD without %<retain%> attribute and %qD with "
"%<retain%> attribute are placed in a section with "
@ -7792,9 +7796,9 @@ switch_to_section (section *new_section, tree decl)
inform (DECL_SOURCE_LOCATION (used_decl),
"%qD was declared here", used_decl);
}
else
return;
}
else if (in_section == new_section)
return;
if (new_section->common.flags & SECTION_FORGET)
in_section = NULL;
@ -8007,7 +8011,7 @@ output_object_block (struct object_block *block)
&& (strcmp (block->sect->named.name, ".vtable_map_vars") == 0))
handle_vtv_comdat_section (block->sect, block->sect->named.decl);
else
switch_to_section (block->sect);
switch_to_section (block->sect, SYMBOL_REF_DECL ((*block->objects)[0]));
gcc_checking_assert (!(block->sect->common.flags & SECTION_MERGE));
assemble_align (block->alignment);