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Support immediate binding option #335

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53b0d91
Implement immediate binding for dynamic linking
DrXiao Sep 9, 2026
0d1e98b
Introduce a Makefile variable to determine the binding strategy
DrXiao Sep 9, 2026
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5 changes: 3 additions & 2 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -53,12 +53,13 @@ BUILTIN_LIBC_HEADER := c.h
STAGE0_FLAGS ?= --dump-ir
STAGE1_FLAGS ?=
DYNLINK ?= 0
BINDING ?= lazy

COMMENTFLOW ?= commentflow
SHFMT ?= shfmt
ifeq ($(DYNLINK),1)
STAGE0_FLAGS += --dynlink
STAGE1_FLAGS += --dynlink
STAGE0_FLAGS += --dynlink -z $(BINDING)
STAGE1_FLAGS += --dynlink -z $(BINDING)

@cubic-dev-ai cubic-dev-ai Bot Sep 9, 2026

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P2: When a BINDING=now build runs make check, the test suite still exercises lazy binding. The check-stage0/check-stage2/check-abi-* targets forward only $(DYNLINK) to the test drivers, and tests/driver.sh compiles its test programs with a plain --dynlink (no -z now), so on arm/riscv those programs default to lazy binding. With this change BINDING becomes a build knob that stage1/stage2 honor, but the tests built by make check never verify the immediate-binding path this PR adds. Forward $(BINDING) (or a corresponding -z flag) to the driver invocations so immediate binding can actually be validated, matching the PR's TODO about CI validation.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At Makefile, line 62:

<comment>When a `BINDING=now` build runs `make check`, the test suite still exercises lazy binding. The `check-stage0`/`check-stage2`/`check-abi-*` targets forward only `$(DYNLINK)` to the test drivers, and `tests/driver.sh` compiles its test programs with a plain `--dynlink` (no `-z now`), so on arm/riscv those programs default to lazy binding. With this change `BINDING` becomes a build knob that stage1/stage2 honor, but the tests built by `make check` never verify the immediate-binding path this PR adds. Forward `$(BINDING)` (or a corresponding `-z` flag) to the driver invocations so immediate binding can actually be validated, matching the PR's TODO about CI validation.</comment>

<file context>
@@ -53,12 +53,13 @@ BUILTIN_LIBC_HEADER := c.h
-    STAGE0_FLAGS += --dynlink
-    STAGE1_FLAGS += --dynlink
+    STAGE0_FLAGS += --dynlink -z $(BINDING)
+    STAGE1_FLAGS += --dynlink -z $(BINDING)
 endif
 
</file context>

endif

SRCS := $(wildcard $(patsubst %,%/main.c, $(SRCDIR)))
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1 change: 0 additions & 1 deletion mk/arm64.mk
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Expand Up @@ -25,7 +25,6 @@ ARCH_DEFS = \
\#define PLT_ENT_SIZE 16\n$\
\#define RESERVED_GOT_NUM 3\n$\
\#define R_ARCH_JUMP_SLOT 1026 /* R_AARCH64_JUMP_SLOT */\n$\
\#define DYN_BIND_NOW 1\n$\
"

# An Arm64 Linux host runs this target's output itself, so nothing has to stand
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1 change: 0 additions & 1 deletion mk/x64.mk
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Expand Up @@ -16,7 +16,6 @@ ARCH_DEFS = \
\#define RESERVED_GOT_NUM 3\n$\
\#define R_ARCH_JUMP_SLOT 7 /* R_X86_64_JUMP_SLOT */\n$\
\#define REG_CNT 11 /* rdi rsi rdx rcx r8 r9 rax rbx r14 r12 r13 */\n$\
\#define DYN_BIND_NOW 1 /* this PLT has no lazy-resolution path */\n$\
\#define HAVE_COND_MOVE 1 /* CMOVcc */\n$\
\#define CALLEE_SAVED_REGS 4 /* the file ends rbx r14 r12 r13 */\n$\
"
7 changes: 0 additions & 7 deletions src/defs.h
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Expand Up @@ -177,13 +177,6 @@
#define ALIGN_UP(val, align) (((val) + (align) - 1) & ~((align) - 1))
#endif

/* Targets whose PLT has no lazy-resolution path ask the loader to bind every
* PLT entry at load time.
*/
#ifndef DYN_BIND_NOW
#define DYN_BIND_NOW 0
#endif

#define ELF_MACHINE_ARM32 0x28
#define ELF_MACHINE_RV32 0xf3
#define ELF_MACHINE_X86_64 0x3e
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11 changes: 7 additions & 4 deletions src/elf.c
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Expand Up @@ -1086,14 +1086,17 @@ void elf_generate_dynamic_sections(void)
elf_write_dyn(dynamic_sections.elf_dynamic, 0x3,
dynamic_sections.elf_got_start);
elf_write_dyn(dynamic_sections.elf_dynamic, 0x1, 0x1);
#if DYN_BIND_NOW == 1

/* Resolve every PLT entry at load time. This target's PLT[0] does not
* arrange the GOT[1]/GOT[2] hand-off the lazy resolver needs, so the loader
* writes the final addresses straight into the GOT instead.
*/
elf_write_dyn(dynamic_sections.elf_dynamic, 0x18, 0x0); /* DT_BIND_NOW */
elf_write_dyn(dynamic_sections.elf_dynamic, 0x1e, 0x8); /* DF_BIND_NOW */
#endif
if (imm_binding) {
elf_write_dyn(dynamic_sections.elf_dynamic, 0x18,
0x0); /* DT_BIND_NOW */
elf_write_dyn(dynamic_sections.elf_dynamic, 0x1e,
0x8); /* DF_BIND_NOW */
}
elf_write_dyn(dynamic_sections.elf_dynamic, 0x0, 0x0);
}

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1 change: 1 addition & 0 deletions src/globals.c
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Expand Up @@ -101,6 +101,7 @@ dynamic_sections_t dynamic_sections;

/* Command line compilation flags */
bool dynlink = false;
bool imm_binding = false;
bool libc = true;
bool expand_only = false;
bool dump_ir = false;
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25 changes: 23 additions & 2 deletions src/main.c
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Expand Up @@ -117,7 +117,17 @@ int main(int argc, char *argv[])
libc = false;
else if (!strcmp(argv[i], "--dynlink"))
dynlink = true;
else if (!strcmp(argv[i], "-E"))
else if (!strcmp(argv[i], "-z")) {
if (i + 1 >= argc)
usage_error("-z requires \"lazy\" or \"now\"");

if (!strcmp(argv[i + 1], "lazy"))
imm_binding = false;
else if (!strcmp(argv[i + 1], "now"))
imm_binding = true;
else
usage_error("-z requires \"lazy\" or \"now\"");
} else if (!strcmp(argv[i], "-E"))
Comment on lines +120 to +130

@cubic-dev-ai cubic-dev-ai Bot Sep 9, 2026

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P2: The -z handler reads argv[i + 1] but never advances i, so its value lazy/now is not consumed and is treated as a positional input on the next loop iteration. Unlike the neighboring -o case (which does i++), this leaves argv[i+1] to hit the trailing else ... in = argv[i] branch. As a result, shecc in.c -z now first sets in = "in.c" and then overwrites it with "now", so the compiler tries to open a file named now and fails; and shecc -z now with no real input never triggers the "Missing source file" error because in is set to "now". Add i++; after the value is consumed, matching the -o handling.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At src/main.c, line 120:

<comment>The `-z` handler reads `argv[i + 1]` but never advances `i`, so its value `lazy`/`now` is not consumed and is treated as a positional input on the next loop iteration. Unlike the neighboring `-o` case (which does `i++`), this leaves `argv[i+1]` to hit the trailing `else ... in = argv[i]` branch. As a result, `shecc in.c -z now` first sets `in = "in.c"` and then overwrites it with `"now"`, so the compiler tries to open a file named `now` and fails; and `shecc -z now` with no real input never triggers the "Missing source file" error because `in` is set to `"now"`. Add `i++;` after the value is consumed, matching the `-o` handling.</comment>

<file context>
@@ -117,7 +117,17 @@ int main(int argc, char *argv[])
         else if (!strcmp(argv[i], "--dynlink"))
             dynlink = true;
-        else if (!strcmp(argv[i], "-E"))
+        else if (!strcmp(argv[i], "-z")) {
+            if (i + 1 >= argc)
+                usage_error("-z requires \"lazy\" or \"now\"");
</file context>
Suggested change
else if (!strcmp(argv[i], "-z")) {
if (i + 1 >= argc)
usage_error("-z requires \"lazy\" or \"now\"");
if (!strcmp(argv[i + 1], "lazy"))
imm_binding = false;
else if (!strcmp(argv[i + 1], "now"))
imm_binding = true;
else
usage_error("-z requires \"lazy\" or \"now\"");
} else if (!strcmp(argv[i], "-E"))
else if (!strcmp(argv[i], "-z")) {
if (i + 1 >= argc)
usage_error("-z requires \"lazy\" or \"now\"");
if (!strcmp(argv[i + 1], "lazy"))
imm_binding = false;
else if (!strcmp(argv[i + 1], "now"))
imm_binding = true;
else
usage_error("-z requires \"lazy\" or \"now\"");
i++;
}

expand_only = true;
else if (!strcmp(argv[i], "-o")) {
if (i + 1 < argc) {
Expand All @@ -131,10 +141,21 @@ int main(int argc, char *argv[])
in = argv[i];
}

if (dynlink) {
switch (ELF_MACHINE) {
/* The following 64-bit targets have no lazy-resolution path, so
* immediate binding must be used.
*/
case ELF_MACHINE_X86_64:
case ELF_MACHINE_AARCH64:
imm_binding = true;
}
}

if (!in) {
printf(
"Usage: shecc [-o output] [+m] [--dot] [--dump-ir] [--no-libc] "
"[--dynlink] [-E] <input.c>\n");
"[--dynlink] [-z <lazy | now>] [-E] <input.c>\n");
usage_error("Missing source file");
}

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