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binutils: MSVC link.exe compatibility (#135)

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Microsoft's link.exe assumes that import libraries carry null terminator
entries and does not add a terminating null entry when building import
tables. When link.exe inputs only Binutils-created import libraries, it
quietly produces corrupt PE images. This patch makes Bintuils add these
null import entries to satisfy link.exe.
This commit is contained in:
Christopher Wellons
2026-07-28 08:57:47 -04:00
parent e11fe5b843
commit 99d35a4683
1 changed files with 99 additions and 0 deletions
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99
src/binutils-null-import-descriptor.patch Normal file
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@@ -0,0 +1,99 @@
Improve Binutils compatability with MSVC link.exe
Microsoft's link.exe assumes that import libraries carry null terminator
entries and does not add a terminating null entry when building import
tables. When link.exe inputs only Binutils-created import libraries, it
quietly produces corrupt PE images. This patch makes Bintuils add these
null import entries to satisfy link.exe.
--- a/binutils/dlltool.c
+++ b/binutils/dlltool.c
@@ -2896,6 +2896,22 @@
temp_file_to_remove[TEMP_TAIL_FILE] = TMP_TAIL_S;
+ /* An import library must supply the null import descriptor that
+ terminates the import directory table. GNU ld emits a terminator
+ itself via its linker script, but MSVC link.exe lays out only what
+ import libraries provide, normally the .idata$3 contribution of
+ the __NULL_IMPORT_DESCRIPTOR archive member. Without these zeros
+ link.exe leaves the descriptor table unterminated, running into
+ whatever .idata$4 data follows. Extra copies from multiple import
+ libraries are harmless: all .idata$3 input sections sort after all
+ descriptors in .idata$2, so the first terminates the table. */
+ fprintf (f, "\t.section\t.idata$3\n");
+ fprintf (f, "\t%s\t0\n", ASM_LONG);
+ fprintf (f, "\t%s\t0\n", ASM_LONG);
+ fprintf (f, "\t%s\t0\n", ASM_LONG);
+ fprintf (f, "\t%s\t0\n", ASM_LONG);
+ fprintf (f, "\t%s\t0\n", ASM_LONG);
+
if (!no_idata4)
{
fprintf (f, "\t.section\t.idata$4\n");
--- a/ld/pe-dll.c
+++ b/ld/pe-dll.c
@@ -2221,8 +2221,14 @@
return abfd;
}
-/* .section .idata$4
+/* .section .idata$3
.long 0
+ .long 0
+ .long 0
+ .long 0
+ .long 0
+ .section .idata$4
+ .long 0
[.long 0] for PE+
.section .idata$5
.long 0
@@ -2235,8 +2241,8 @@
static bfd *
make_tail (bfd *parent)
{
- asection *id4, *id5, *id7;
- unsigned char *d4, *d5, *d7;
+ asection *id3, *id4, *id5, *id7;
+ unsigned char *d3, *d4, *d5, *d7;
int len;
char *oname;
bfd *abfd;
@@ -2253,12 +2259,27 @@
bfd_set_arch_mach (abfd, pe_details->bfd_arch, 0);
symptr = 0;
- symtab = xmalloc (5 * sizeof (asymbol *));
+ symtab = xmalloc (6 * sizeof (asymbol *));
+ id3 = quick_section (abfd, ".idata$3", SEC_HAS_CONTENTS, 2);
id4 = quick_section (abfd, ".idata$4", SEC_HAS_CONTENTS, 2);
id5 = quick_section (abfd, ".idata$5", SEC_HAS_CONTENTS, 2);
id7 = quick_section (abfd, ".idata$7", SEC_HAS_CONTENTS, 2);
quick_symbol (abfd, U (""), dll_symname, "_iname", id7, BSF_GLOBAL, 0);
+ /* An import library must supply the null import descriptor that
+ terminates the import directory table. GNU ld emits a terminator
+ itself via its linker script, but MSVC link.exe lays out only what
+ import libraries provide, normally the .idata$3 contribution of
+ the __NULL_IMPORT_DESCRIPTOR archive member. Without these zeros
+ link.exe leaves the descriptor table unterminated, running into
+ whatever .idata$4 data follows. Extra copies from multiple import
+ libraries are harmless: all .idata$3 input sections sort after all
+ descriptors in .idata$2, so the first terminates the table. */
+ bfd_set_section_size (id3, 20);
+ d3 = xmalloc (20);
+ id3->contents = d3;
+ memset (d3, 0, 20);
+
bfd_set_section_size (id4, PE_IDATA4_SIZE);
d4 = xmalloc (PE_IDATA4_SIZE);
id4->contents = d4;
@@ -2283,6 +2304,7 @@
bfd_set_symtab (abfd, symtab, symptr);
+ bfd_set_section_contents (abfd, id3, d3, 0, 20);
bfd_set_section_contents (abfd, id4, d4, 0, PE_IDATA4_SIZE);
bfd_set_section_contents (abfd, id5, d5, 0, PE_IDATA5_SIZE);
bfd_set_section_contents (abfd, id7, d7, 0, len);