[Patch mach-o/bfd] improve build command routine robustness.
Iain Sandoe
developer@sandoe-acoustics.co.uk
Mon Jan 9 11:01:00 GMT 2012
Although I do not see the reported build warning with 4.6 or 4.7 as
the host compiler, I can see where it could arise.
Additionally, when looking harder at this, it seems that almost any
permutation of commands is valid - the following patch improves
robustness - and should fix the reported warning.
OK?
Iain
bfd:
* mach-o.c (bfd_mach_o_build_commands): Make the building of each
command
type independent.
bfd/mach-o.c | 129 ++++++++++++++++++++++++++++++++++
+----------------------
1 files changed, 79 insertions(+), 50 deletions(-)
diff --git a/bfd/mach-o.c b/bfd/mach-o.c
index 07ca65a..a1f6596 100644
--- a/bfd/mach-o.c
+++ b/bfd/mach-o.c
@@ -2149,15 +2149,19 @@ bfd_mach_o_build_dysymtab_command (bfd *abfd,
TODO: Other file formats, rebuilding symtab/dysymtab commands for
strip
and copy functionality. */
+#define MACHO_SEG_CMD_PRESENT 0x0001
+#define MACHO_SYM_CMD_PRESENT 0x0002
+#define MACHO_DYSYM_CMD_PRESENT 0x0004
+
bfd_boolean
bfd_mach_o_build_commands (bfd *abfd)
{
bfd_mach_o_data_struct *mdata = bfd_mach_o_get_data (abfd);
- unsigned int wide = mach_o_wide_p (&mdata->header);
- bfd_mach_o_segment_command *seg;
- bfd_mach_o_load_command *cmd;
- bfd_mach_o_load_command *symtab_cmd;
- unsigned symcind;
+ unsigned wide = mach_o_wide_p (&mdata->header);
+ unsigned present = 0;
+ unsigned symind = 0;
+ unsigned dysymind = 0;
+ unsigned long base_offset = 0;
/* Return now if commands are already present. */
if (mdata->header.ncmds)
@@ -2187,31 +2191,49 @@ bfd_mach_o_build_commands (bfd *abfd)
if (!bfd_mach_o_mangle_symbols (abfd))
return FALSE;
- /* It's valid to have a file with only absolute symbols... */
+ /* Very simple command set (only really applicable to MH_OBJECTs):
+ All the commands are optional - present only when there is
suitable data.
+ (i.e. it is valid to have an empty file)
+
+ a command (segment) to contain all the sections,
+ command for the symbol table,
+ a command for the dysymtab.
+
+ ??? maybe we should assert that this is an MH_OBJECT? */
+
if (mdata->nsects > 0)
{
mdata->header.ncmds = 1;
- symcind = 1;
+ symind = 1;
+ dysymind = 1;
+ present |= MACHO_SEG_CMD_PRESENT;
}
- else
- symcind = 0;
- /* It's OK to have a file with only section statements. */
if (bfd_get_symcount (abfd) > 0)
- mdata->header.ncmds += 1;
+ {
+ mdata->header.ncmds += 1;
+ dysymind += 1;
+ present |= MACHO_SYM_CMD_PRESENT;
+ }
- /* Very simple version (only really applicable to MH_OBJECTs):
- a command (segment) to contain all the sections,
- a command for the symbol table
- a n (optional) command for the dysymtab.
+ /* FIXME:
+ This is a rather crude test for whether we should build a
dysymtab. */
+ if (bfd_mach_o_should_emit_dysymtab ()
+ && bfd_get_symcount (abfd))
+ {
+ mdata->header.ncmds += 1;
+ present |= MACHO_DYSYM_CMD_PRESENT;
+ }
- ??? maybe we should assert that this is an MH_OBJECT? */
+ if (wide)
+ base_offset = BFD_MACH_O_HEADER_64_SIZE;
+ else
+ base_offset = BFD_MACH_O_HEADER_SIZE;
- if (bfd_mach_o_should_emit_dysymtab ()
- && bfd_get_symcount (abfd) > 0)
- mdata->header.ncmds += 1;
+ /* Well, we must have a header, at least. */
+ mdata->filelen = base_offset;
- /* A bit weird, but looks like no content;
+ /* A bit unusual, but no content is valid;
as -n empty.s -o empty.o */
if (mdata->header.ncmds == 0)
return TRUE;
@@ -2221,10 +2243,10 @@ bfd_mach_o_build_commands (bfd *abfd)
if (mdata->commands == NULL)
return FALSE;
- if (mdata->nsects > 0)
+ if (present & MACHO_SEG_CMD_PRESENT)
{
- cmd = &mdata->commands[0];
- seg = &cmd->command.segment;
+ bfd_mach_o_load_command *cmd = &mdata->commands[0];
+ bfd_mach_o_segment_command *seg = &cmd->command.segment;
/* Count the segctions in the special blank segment used for
MH_OBJECT. */
seg->nsects = bfd_mach_o_count_sections_for_seg (NULL, mdata);
@@ -2232,50 +2254,57 @@ bfd_mach_o_build_commands (bfd *abfd)
return FALSE;
/* Init segment command. */
+ cmd->offset = base_offset;
if (wide)
{
cmd->type = BFD_MACH_O_LC_SEGMENT_64;
- cmd->offset = BFD_MACH_O_HEADER_64_SIZE;
cmd->len = BFD_MACH_O_LC_SEGMENT_64_SIZE
+ BFD_MACH_O_SECTION_64_SIZE * seg->nsects;
}
else
{
cmd->type = BFD_MACH_O_LC_SEGMENT;
- cmd->offset = BFD_MACH_O_HEADER_SIZE;
cmd->len = BFD_MACH_O_LC_SEGMENT_SIZE
+ BFD_MACH_O_SECTION_SIZE * seg->nsects;
}
+
cmd->type_required = FALSE;
mdata->header.sizeofcmds = cmd->len;
- mdata->filelen = cmd->offset + cmd->len;
+ mdata->filelen += cmd->len;
}
- if (bfd_get_symcount (abfd) > 0)
+ if (present & MACHO_SYM_CMD_PRESENT)
{
/* Init symtab command. */
- symtab_cmd = &mdata->commands[symcind];
-
- symtab_cmd->type = BFD_MACH_O_LC_SYMTAB;
- if (symcind > 0)
- symtab_cmd->offset = mdata->commands[0].offset
- + mdata->commands[0].len;
- else
- symtab_cmd->offset = 0;
- symtab_cmd->len = 6 * 4;
- symtab_cmd->type_required = FALSE;
+ bfd_mach_o_load_command *cmd = &mdata->commands[symind];
- mdata->header.sizeofcmds += symtab_cmd->len;
- mdata->filelen += symtab_cmd->len;
+ cmd->type = BFD_MACH_O_LC_SYMTAB;
+ cmd->offset = base_offset;
+ if (present & MACHO_SEG_CMD_PRESENT)
+ cmd->offset += mdata->commands[0].len;
+
+ cmd->len = 6 * 4;
+ cmd->type_required = FALSE;
+ mdata->header.sizeofcmds += cmd->len;
+ mdata->filelen += cmd->len;
}
- /* If required, setup symtab command. */
- if (bfd_mach_o_should_emit_dysymtab ()
- && bfd_get_symcount (abfd) > 0)
+ /* If required, setup symtab command, see comment above about the
quality
+ of this test. */
+ if (present & MACHO_DYSYM_CMD_PRESENT)
{
- cmd = &mdata->commands[symcind+1];
+ bfd_mach_o_load_command *cmd = &mdata->commands[dysymind];
+
cmd->type = BFD_MACH_O_LC_DYSYMTAB;
- cmd->offset = symtab_cmd->offset + symtab_cmd->len;
+ if (present & MACHO_SYM_CMD_PRESENT)
+ cmd->offset = mdata->commands[symind].offset
+ + mdata->commands[symind].len;
+ else if (present & MACHO_SEG_CMD_PRESENT)
+ cmd->offset = mdata->commands[0].offset
+ + mdata->commands[0].len;
+ else
+ cmd->offset = base_offset;
+
cmd->type_required = FALSE;
cmd->len = 18 * 4 + BFD_MACH_O_LC_SIZE;
@@ -2285,18 +2314,18 @@ bfd_mach_o_build_commands (bfd *abfd)
/* So, now we have sized the commands and the filelen set to that.
Now we can build the segment command and set the section file
offsets. */
- if (mdata->nsects > 0
- && ! bfd_mach_o_build_seg_command (NULL, mdata, seg))
+ if ((present & MACHO_SEG_CMD_PRESENT)
+ && ! bfd_mach_o_build_seg_command (NULL, mdata,
+ &mdata->commands[0].command.segment))
return FALSE;
/* If we're doing a dysymtab, cmd points to its load command. */
- if (bfd_mach_o_should_emit_dysymtab ()
- && bfd_get_symcount (abfd) > 0
+ if ((present & MACHO_DYSYM_CMD_PRESENT)
&& ! bfd_mach_o_build_dysymtab_command (abfd, mdata,
- &mdata->commands[symcind+1]))
+ &mdata->commands[dysymind]))
return FALSE;
- /* The symtab command is filled in when the symtab is written. */
+ /* The symtab command is filled when the symtab is written. */
return TRUE;
}
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