[gcc r11-6141] Warn used and not used symbols in section with the same name

[gcc r11-6141] Warn used and not used symbols in section with the same name

[H.J. Lu]

https://gcc.gnu.org/g:2a976020603589e897fcfa3276590ef50b489d34

commit r11-6141-g2a976020603589e897fcfa3276590ef50b489d34
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Thu Dec 3 15:39:59 2020 -0800

    Warn used and not used symbols in section with the same name
    
    When SECTION_RETAIN is used, issue a warning when a symbol without used
    attribute and a symbol with used attribute are placed in the section with
    the same name, like
    
    int __attribute__((used,section(".data.foo"))) foo2 = 2;
    int __attribute__((section(".data.foo"))) foo1 = 1;
    
    since assembler will put them in different sections with the same section
    name.
    
    gcc/
    
            PR target/98146
            * varasm.c (switch_to_section): Warn when a symbol without used
            attribute and a symbol with used attribute are placed in the
            section with the same name.
    
    gcc/testsuite/
    
            PR target/98146
            * c-c++-common/attr-used-5.c: Updated.
            * c-c++-common/attr-used-6.c: Likewise.
            * c-c++-common/attr-used-7.c: Likewise.
            * c-c++-common/attr-used-8.c: Likewise.

Diff:
---
 gcc/testsuite/c-c++-common/attr-used-5.c |  1 +
 gcc/testsuite/c-c++-common/attr-used-6.c |  1 +
 gcc/testsuite/c-c++-common/attr-used-7.c |  1 +
 gcc/testsuite/c-c++-common/attr-used-8.c |  1 +
 gcc/varasm.c                             | 22 +++++++++++++++++++---
 5 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/gcc/testsuite/c-c++-common/attr-used-5.c b/gcc/testsuite/c-c++-common/attr-used-5.c
index 9fc0d3834e9..ba59326e452 100644
--- a/gcc/testsuite/c-c++-common/attr-used-5.c
+++ b/gcc/testsuite/c-c++-common/attr-used-5.c
@@ -10,6 +10,7 @@ extern struct dtv_slotinfo_list *list;
 
 static int __attribute__ ((section ("__libc_freeres_fn")))
 free_slotinfo (struct dtv_slotinfo_list **elemp)
+/* { dg-warning "'.*' without 'used' attribute and '.*' with 'used' attribute are placed in a section with the same name" "" { target R_flag_in_section } .-1 } */
 {
   if (!free_slotinfo (&(*elemp)->next))
     return 0;
diff --git a/gcc/testsuite/c-c++-common/attr-used-6.c b/gcc/testsuite/c-c++-common/attr-used-6.c
index 0cb82ade5a9..5d20f875bf0 100644
--- a/gcc/testsuite/c-c++-common/attr-used-6.c
+++ b/gcc/testsuite/c-c++-common/attr-used-6.c
@@ -18,6 +18,7 @@ free_slotinfo (struct dtv_slotinfo_list **elemp)
 
 __attribute__ ((section ("__libc_freeres_fn")))
 void free_mem (void)
+/* { dg-warning "'.*' without 'used' attribute and '.*' with 'used' attribute are placed in a section with the same name" "" { target R_flag_in_section } .-1 } */
 {
   free_slotinfo (&list);
 }
diff --git a/gcc/testsuite/c-c++-common/attr-used-7.c b/gcc/testsuite/c-c++-common/attr-used-7.c
index fba2706ffc1..75576bcabe5 100644
--- a/gcc/testsuite/c-c++-common/attr-used-7.c
+++ b/gcc/testsuite/c-c++-common/attr-used-7.c
@@ -3,6 +3,7 @@
 
 int __attribute__((used,section(".data.foo"))) foo2 = 2;
 int __attribute__((section(".data.foo"))) foo1 = 1;
+/* { dg-warning "'.*' without 'used' attribute and '.*' with 'used' 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 } } } */
diff --git a/gcc/testsuite/c-c++-common/attr-used-8.c b/gcc/testsuite/c-c++-common/attr-used-8.c
index 4da4aabe573..e4982db1044 100644
--- a/gcc/testsuite/c-c++-common/attr-used-8.c
+++ b/gcc/testsuite/c-c++-common/attr-used-8.c
@@ -2,6 +2,7 @@
 /* { dg-options "-Wall -O2" } */
 
 int __attribute__((section(".data.foo"))) foo1 = 1;
+/* { dg-warning "'.*' without 'used' attribute and '.*' with 'used' attribute are placed in a section with the same name" "" { target R_flag_in_section } .-1 } */
 int __attribute__((used,section(".data.foo"))) foo2 = 2;
 
 /* { dg-final { scan-assembler ".data.foo,\"aw\"" { target R_flag_in_section } } } */
diff --git a/gcc/varasm.c b/gcc/varasm.c
index cfec870e067..a1a8d3bd73e 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -7765,11 +7765,27 @@ switch_to_section (section *new_section, tree decl)
 	{
 	  /* If the SECTION_RETAIN bit doesn't match, switch to a new
 	     section.  */
+	  tree used_decl, no_used_decl;
+
 	  if (DECL_PRESERVE_P (decl))
-	    new_section->common.flags |= SECTION_RETAIN;
+	    {
+	      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);
+	    {
+	      new_section->common.flags &= ~(SECTION_RETAIN
+					     | SECTION_DECLARED);
+	      used_decl = new_section->named.decl;
+	      no_used_decl = decl;
+	    }
+	  warning (OPT_Wattributes,
+		   "%+qD without %<used%> attribute and %qD with "
+		   "%<used%> attribute are placed in a section with "
+		   "the same name", no_used_decl, used_decl);
+	  inform (DECL_SOURCE_LOCATION (used_decl),
+		  "%qD was declared here", used_decl);
 	}
       else
 	return;