https://sourceware.org/bugzilla/show_bug.cgi?id=27472
Bug ID: 27472
Summary: gas: Suppress "CFI instruction used without previous
.cfi_startproc" if .cfi_sections is empty
Product: binutils
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: gas
Assignee: unassigned at sourceware dot org
Reporter: i at maskray dot me
Target Milestone: ---
% cat a.c
int main() {
asm("pushl 0\n.cfi_adjust_cfa_offset 4\npop %%eax\n.cfi_adjust_cfa_offset -4"
::: "eax");
}
% gcc -m32 -c -fomit-frame-pointer -fno-asynchronous-unwind-tables a.c
a.c: Assembler messages:
a.c:3: Error: CFI instruction used without previous .cfi_startproc
a.c:5: Error: CFI instruction used without previous .cfi_startproc
-fasynchronous-unwind-tables & -fno-asynchronous-unwind-tables do not have a
predefined macro, so it is difficult for the inline asm to know whether CFI
directives should be used. For ergonomics, users just want to write CFI
directives and hope they will be silently ignored in
-fno-asynchronous-unwind-tables mode. However, GNU as errors for .cfi_* without
.cfi_startproc .
I suggest that (1) GCC emits ".cfi_sections" (no value) at the beginning, (2)
GNU as suppresses the error if no .eh_frame/.debug_frame is needed.
The place to patch is gas/dw2gencfi.c:dot_cfi and a few other functions.
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