tools/lib/bpf/elf.c | 8 ++++++++ 1 file changed, 8 insertions(+)
In `elf_close`, we get this with GCC 15 -O3 (at least):
```
In function ‘elf_close’,
inlined from ‘elf_close’ at elf.c:53:6,
inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized]
57 | elf_end(elf_fd->elf);
| ^~~~~~~~~~~~~~~~~~~~
elf.c: In function ‘elf_find_func_offset_from_file’:
elf.c:377:23: note: ‘elf_fd.elf’ was declared here
377 | struct elf_fd elf_fd;
| ^~~~~~
In function ‘elf_close’,
inlined from ‘elf_close’ at elf.c:53:6,
inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized]
58 | close(elf_fd->fd);
| ^~~~~~~~~~~~~~~~~
elf.c: In function ‘elf_find_func_offset_from_file’:
elf.c:377:23: note: ‘elf_fd.fd’ was declared here
377 | struct elf_fd elf_fd;
| ^~~~~~
```
In reality, our use is fine, it's just that GCC doesn't model errno
here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly.
Link: https://gcc.gnu.org/PR114952
Signed-off-by: Sam James <sam@gentoo.org>
---
v2: Fix Clang build.
Range-diff against v1:
1: 3ebbe7a4e93a ! 1: 8f5c3b173e4c libbpf: workaround -Wmaybe-uninitialized false positive
@@ tools/lib/bpf/elf.c: long elf_find_func_offset(Elf *elf, const char *binary_path
return ret;
}
++#if !defined(__clang__)
+#pragma GCC diagnostic push
+/* https://gcc.gnu.org/PR114952 */
+#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
++#endif
/* Find offset of function name in ELF object specified by path. "name" matches
* symbol name or name@@LIB for library functions.
*/
@@ tools/lib/bpf/elf.c: long elf_find_func_offset_from_file(const char *binary_path
elf_close(&elf_fd);
return ret;
}
++#if !defined(__clang__)
+#pragma GCC diagnostic pop
++#endif
struct symbol {
const char *name;
tools/lib/bpf/elf.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index c92e02394159..7058425ca85b 100644
--- a/tools/lib/bpf/elf.c
+++ b/tools/lib/bpf/elf.c
@@ -369,6 +369,11 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
return ret;
}
+#if !defined(__clang__)
+#pragma GCC diagnostic push
+/* https://gcc.gnu.org/PR114952 */
+#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
/* Find offset of function name in ELF object specified by path. "name" matches
* symbol name or name@@LIB for library functions.
*/
@@ -384,6 +389,9 @@ long elf_find_func_offset_from_file(const char *binary_path, const char *name)
elf_close(&elf_fd);
return ret;
}
+#if !defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
struct symbol {
const char *name;
--
2.45.2
On 09/08/2024 18:26, Sam James wrote:
> In `elf_close`, we get this with GCC 15 -O3 (at least):
> ```
> In function ‘elf_close’,
> inlined from ‘elf_close’ at elf.c:53:6,
> inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized]
> 57 | elf_end(elf_fd->elf);
> | ^~~~~~~~~~~~~~~~~~~~
> elf.c: In function ‘elf_find_func_offset_from_file’:
> elf.c:377:23: note: ‘elf_fd.elf’ was declared here
> 377 | struct elf_fd elf_fd;
> | ^~~~~~
> In function ‘elf_close’,
> inlined from ‘elf_close’ at elf.c:53:6,
> inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized]
> 58 | close(elf_fd->fd);
> | ^~~~~~~~~~~~~~~~~
> elf.c: In function ‘elf_find_func_offset_from_file’:
> elf.c:377:23: note: ‘elf_fd.fd’ was declared here
> 377 | struct elf_fd elf_fd;
> | ^~~~~~
> ```
>
> In reality, our use is fine, it's just that GCC doesn't model errno
> here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly.
>
> Link: https://gcc.gnu.org/PR114952
> Signed-off-by: Sam James <sam@gentoo.org>
> ---
> v2: Fix Clang build.
>
> Range-diff against v1:
> 1: 3ebbe7a4e93a ! 1: 8f5c3b173e4c libbpf: workaround -Wmaybe-uninitialized false positive
> @@ tools/lib/bpf/elf.c: long elf_find_func_offset(Elf *elf, const char *binary_path
> return ret;
> }
>
> ++#if !defined(__clang__)
> +#pragma GCC diagnostic push
> +/* https://gcc.gnu.org/PR114952 */
> +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
> ++#endif
> /* Find offset of function name in ELF object specified by path. "name" matches
> * symbol name or name@@LIB for library functions.
> */
> @@ tools/lib/bpf/elf.c: long elf_find_func_offset_from_file(const char *binary_path
> elf_close(&elf_fd);
> return ret;
> }
> ++#if !defined(__clang__)
> +#pragma GCC diagnostic pop
> ++#endif
>
> struct symbol {
> const char *name;
>
> tools/lib/bpf/elf.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> index c92e02394159..7058425ca85b 100644
> --- a/tools/lib/bpf/elf.c
> +++ b/tools/lib/bpf/elf.c
> @@ -369,6 +369,11 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
> return ret;
> }
>
> +#if !defined(__clang__)
> +#pragma GCC diagnostic push
> +/* https://gcc.gnu.org/PR114952 */
> +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
> +#endif
> /* Find offset of function name in ELF object specified by path. "name" matches
> * symbol name or name@@LIB for library functions.
> */
> @@ -384,6 +389,9 @@ long elf_find_func_offset_from_file(const char *binary_path, const char *name)
> elf_close(&elf_fd);
> return ret;
> }
> +#if !defined(__clang__)
> +#pragma GCC diagnostic pop
> +#endif
>
> struct symbol {
> const char *name;
Would just initializing struct elf_fd be enough to silence the error
perhaps, i.e.
diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index c92e02394159..3060597a527e 100644
--- a/tools/lib/bpf/elf.c
+++ b/tools/lib/bpf/elf.c
@@ -374,7 +374,7 @@ long elf_find_func_offset(Elf *elf, const char
*binary_path, const char *name)
*/
long elf_find_func_offset_from_file(const char *binary_path, const char
*name)
{
- struct elf_fd elf_fd;
+ struct elf_fd elf_fd = { .fd = -1 };
long ret = -ENOENT;
ret = elf_open(binary_path, &elf_fd);
Alan Maguire <alan.maguire@oracle.com> writes: > On 09/08/2024 18:26, Sam James wrote: >> In `elf_close`, we get this with GCC 15 -O3 (at least): > [...] > > Would just initializing struct elf_fd be enough to silence the error > perhaps, i.e. Yeah, that WFM. Thanks, sent v3.
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