[PATCH 1/3] mkimage: Fix dangling pointer may be used error

[Michael Chang]

The warning is real as long as dangling pointer to 'tmp_' may be used if
o32 and o64 are both null. However that is not going to happen and can
be ignored safely because the PE_OHDR is being used in a context that
either o32 or o64 must have been properly initialized. Sadly compiler
seems not to always optimize that unused _tmp away so explicit
suppression remain needed here.

../util/mkimage.c: In function 'grub_install_generate_image':
../util/mkimage.c:1422:41: error: dangling pointer to 'tmp_' may be used 
[-Werror=dangling-pointer=]
 1422 |         PE_OHDR (o32, o64, header_size) = grub_host_to_target32 
(header_size);
../util/mkimage.c:857:28: note: 'tmp_' declared here
  857 |   __typeof__((o64)->field) tmp_;                \
      |                            ^~~~

Signed-off-by: Michael Chang <mchang@suse.com>
---
 util/mkimage.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/util/mkimage.c b/util/mkimage.c
index 21c2db7362..43078c71cd 100644
--- a/util/mkimage.c
+++ b/util/mkimage.c
@@ -1383,6 +1383,10 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
            section = (struct grub_pe32_section_table *)(o64 + 1);
          }
 
+#if __GNUC__ >= 12
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-pointer"
+#endif
        PE_OHDR (o32, o64, header_size) = grub_host_to_target32 (header_size);
        PE_OHDR (o32, o64, entry_addr) = grub_host_to_target32 
(layout.start_address);
        PE_OHDR (o32, o64, image_base) = 0;
@@ -1402,6 +1406,9 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
        /* The sections.  */
        PE_OHDR (o32, o64, code_base) = grub_host_to_target32 (vma);
        PE_OHDR (o32, o64, code_size) = grub_host_to_target32 
(layout.exec_size);
+#if __GNUC__ >= 12
+#pragma GCC diagnostic pop
+#endif
        section = init_pe_section (image_target, section, ".text",
                                   &vma, layout.exec_size,
                                   image_target->section_align,
@@ -1411,10 +1418,17 @@ grub_install_generate_image (const char *dir, const 
char *prefix,
                                   GRUB_PE32_SCN_MEM_READ);
 
        scn_size = ALIGN_UP (layout.kernel_size - layout.exec_size, 
GRUB_PE32_FILE_ALIGNMENT);
+#if __GNUC__ >= 12
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-pointer"
+#endif
        /* ALIGN_UP (sbat_size, GRUB_PE32_FILE_ALIGNMENT) is done earlier. */
        PE_OHDR (o32, o64, data_size) = grub_host_to_target32 (scn_size + 
sbat_size +
                                                               ALIGN_UP 
(total_module_size,
                                                                         
GRUB_PE32_FILE_ALIGNMENT));
+#if __GNUC__ >= 12
+#pragma GCC diagnostic pop
+#endif
 
        section = init_pe_section (image_target, section, ".data",
                                   &vma, scn_size, image_target->section_align,
@@ -1445,8 +1459,15 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
          }
 
        scn_size = layout.reloc_size;
+#if __GNUC__ >= 12
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-pointer"
+#endif
        PE_OHDR (o32, o64, base_relocation_table.rva) = grub_host_to_target32 
(vma);
        PE_OHDR (o32, o64, base_relocation_table.size) = grub_host_to_target32 
(scn_size);
+#if __GNUC__ >= 12
+#pragma GCC diagnostic pop
+#endif
        memcpy (pe_img + raw_data, layout.reloc_section, scn_size);
        init_pe_section (image_target, section, ".reloc",
                         &vma, scn_size, image_target->section_align,
-- 
2.34.1