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ae0d2244a2
When BPF object files are linked with bpftool, every symbol must be
accompanied by BTF info. Ensure that extern functions referenced by
global variable initializers are included in BTF.
The primary motivation is "static" initialization of PROG maps:
```c
extern int elsewhere(struct xdp_md *);
struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(max_entries, 1);
__type(key, int);
__type(value, int);
__array(values, int (struct xdp_md *));
} prog_map SEC(".maps") = { .values = { elsewhere } };
```
BPF backend needs debug info to produce BTF. Debug info is not
normally generated for external variables and functions. Previously, it
was solved differently for variables (collecting variable declarations
in ExternalDeclarations vector) and functions (logic invoked during
codegen in CGExpr.cpp).
This patch generalises ExternalDefclarations to include both function
and variable declarations. This change ensures that function references
are not missed no matter the context. Previously external functions
referenced in constant expressions lacked debug info.
10 lines
374 B
C
10 lines
374 B
C
// RUN: %clang -g -target bpf -S -emit-llvm %s -o - | FileCheck %s
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//
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// When linking BPF object files via bpftool, BTF info is required for
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// every symbol. BTF is generated from debug info. Ensure that debug info
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// is emitted for extern functions referenced via variable initializers.
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//
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// CHECK: !DISubprogram(name: "fn"
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extern void fn(void);
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void (*pfn) (void) = &fn;
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