[nasm:master] outmacho: if .rodata contains no relocations, change it to __TEXT, __const

[nasm-bot f. H. P. A. <hp...@li...>]

Commit-ID:  6fc2b123afaaf57577581a7680aa41fe101fd86b
Gitweb:     http://repo.or.cz/w/nasm.git?a=commitdiff;h=6fc2b123afaaf57577581a7680aa41fe101fd86b
Author:     H. Peter Anvin <hp...@li...>
AuthorDate: Tue, 16 Feb 2016 12:56:27 -0800
Committer:  H. Peter Anvin <hp...@li...>
CommitDate: Tue, 16 Feb 2016 12:56:27 -0800

outmacho: if .rodata contains no relocations, change it to __TEXT,__const

If we specify .rodata as opposed to the explicit __DATA,__const, and
we end up with no relocations, change it to __TEXT,__const per the
Mach-O ABI.  However, it is generally better for the programmer to
explicitly specify the items that should go into __TEXT,__const as
otherwise a single relocatable item will force the whole thing into
__DATA.

Signed-off-by: H. Peter Anvin <hp...@li...>


---
 output/outmacho.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/output/outmacho.c b/output/outmacho.c
index e39d655..6872a7b 100644
--- a/output/outmacho.c
+++ b/output/outmacho.c
@@ -114,6 +114,7 @@ struct section {
     int32_t index;
     struct reloc *relocs;
     int align;
+    bool by_name;		/* This section was specified by full MachO name */
 
     /* data that goes into the file */
     char sectname[16];          /* what this section is called */
@@ -248,7 +249,6 @@ static uint64_t seg_vmsize = 0;
 static uint32_t seg_nsects = 0;
 static uint64_t rel_padcnt = 0;
 
-
 #define xstrncpy(xdst, xsrc)						\
     memset(xdst, '\0', sizeof(xdst));	/* zero out whole buffer */	\
     strncpy(xdst, xsrc, sizeof(xdst));	/* copy over string */		\
@@ -632,14 +632,14 @@ static int32_t macho_section(char *name, int pass, int *bits)
 	len = strlen(segment);
 	if (len == 0) {
 	    nasm_error(ERR_NONFATAL, "empty segment name\n");
-	} else if (len > 16) {
+	} else if (len >= 16) {
 	    nasm_error(ERR_NONFATAL, "segment name %s too long\n", segment);
 	}
 
 	len = strlen(section);
 	if (len == 0) {
 	    nasm_error(ERR_NONFATAL, "empty section name\n");
-	} else if (len > 16) {
+	} else if (len >= 16) {
 	    nasm_error(ERR_NONFATAL, "section name %s too long\n", section);
 	}
 
@@ -682,6 +682,7 @@ static int32_t macho_section(char *name, int pass, int *bits)
 	s->align = -1;
 	s->pad = -1;
 	s->offset = -1;
+	s->by_name = false;
 
 	xstrncpy(s->segname, segment);
 	xstrncpy(s->sectname, section);
@@ -697,6 +698,8 @@ static int32_t macho_section(char *name, int pass, int *bits)
     if (comma)
 	*comma = ',';		/* Restore comma */
 
+    s->by_name = s->by_name || comma; /* Was specified by name */
+
     flags = (uint32_t)-1;
 
     while ((NULL != sectionAttributes)
@@ -1114,6 +1117,17 @@ static uint32_t macho_write_segment (uint64_t offset)
 	    s->flags |= S_ATTR_LOC_RELOC;
 	    if (s->extreloc)
 		s->flags |= S_ATTR_EXT_RELOC;
+	} else if (!strcmp(s->segname, "__DATA") &&
+		   !strcmp(s->sectname, "__const") &&
+		   !s->by_name &&
+		   !get_section_by_name("__TEXT", "__const")) {
+	    /*
+	     * The MachO equivalent to .rodata can be either
+	     * __DATA,__const or __TEXT,__const; the latter only if
+	     * there are no relocations.  However, when mixed it is
+	     * better to specify the segments explicitly.
+	     */
+	    xstrncpy(s->segname, "__TEXT");
 	}
 
         fwriteint32_t(s->flags, ofile);      /* flags */