configure: Fix check for INSERT in linker script

Message ID 20210910005051.2120865-1-maskray@google.com
State New
Headers show
Series
  • configure: Fix check for INSERT in linker script
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Commit Message

GCC/Clang use local access when referencing a const variable,
so the conftest.so may have no dynamic relocation.
LLD reports `error: unable to insert .foo after .rela.dyn` when the
destination section does not exist.

Use a non-const int to ensure that .rela.dyn exists.
---
 configure    | 2 +-
 configure.ac | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

-- 
2.33.0.309.g3052b89438-goog

Comments

Siddhesh Poyarekar Sept. 13, 2021, 1:58 p.m. | #1
On 9/10/21 6:20 AM, Fangrui Song via Libc-alpha wrote:
> GCC/Clang use local access when referencing a const variable,

> so the conftest.so may have no dynamic relocation.

> LLD reports `error: unable to insert .foo after .rela.dyn` when the

> destination section does not exist.

> 

> Use a non-const int to ensure that .rela.dyn exists.

> ---

>   configure    | 2 +-

>   configure.ac | 2 +-

>   2 files changed, 2 insertions(+), 2 deletions(-)

> 

> diff --git a/configure b/configure

> index 542802ad35..39d75eb4ed 100755

> --- a/configure

> +++ b/configure

> @@ -5793,7 +5793,7 @@ if ${libc_cv_insert+:} false; then :

>     $as_echo_n "(cached) " >&6

>   else

>     cat > conftest.c <<EOF

> -		const int __attribute__ ((section(".bar"))) bar = 0x12345678;

> +		int __attribute__ ((section(".bar"))) bar = 0x12345678;

>   		int test (void) { return bar; }

>   EOF

>   		cat > conftest.t <<EOF

> diff --git a/configure.ac b/configure.ac

> index d9232418de..00f49f09f7 100644

> --- a/configure.ac

> +++ b/configure.ac

> @@ -1217,7 +1217,7 @@ AC_SUBST(libc_cv_protected_data)

>   AC_CACHE_CHECK(linker support for INSERT in linker script,

>   	       libc_cv_insert,

>   	       [cat > conftest.c <<EOF

> -		const int __attribute__ ((section(".bar"))) bar = 0x12345678;

> +		int __attribute__ ((section(".bar"))) bar = 0x12345678;

>   		int test (void) { return bar; }

>   EOF

>   		cat > conftest.t <<EOF

> 


LGTM.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Patch

diff --git a/configure b/configure
index 542802ad35..39d75eb4ed 100755
--- a/configure
+++ b/configure
@@ -5793,7 +5793,7 @@  if ${libc_cv_insert+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   cat > conftest.c <<EOF
-		const int __attribute__ ((section(".bar"))) bar = 0x12345678;
+		int __attribute__ ((section(".bar"))) bar = 0x12345678;
 		int test (void) { return bar; }
 EOF
 		cat > conftest.t <<EOF
diff --git a/configure.ac b/configure.ac
index d9232418de..00f49f09f7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1217,7 +1217,7 @@  AC_SUBST(libc_cv_protected_data)
 AC_CACHE_CHECK(linker support for INSERT in linker script,
 	       libc_cv_insert,
 	       [cat > conftest.c <<EOF
-		const int __attribute__ ((section(".bar"))) bar = 0x12345678;
+		int __attribute__ ((section(".bar"))) bar = 0x12345678;
 		int test (void) { return bar; }
 EOF
 		cat > conftest.t <<EOF