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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.
12 lines
343 B
C
12 lines
343 B
C
// RUN: %clang -g -target bpf -S -emit-llvm %s -o - | FileCheck %s
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//
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// No debug info is produced for unreferenced functions.
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// CHECK-NOT: !DISubprogram
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void unref(void);
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void unref2(typeof(unref));
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// No debug info for unused extern variables as well.
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// CHECK-NOT: !DiGlobalVariable
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extern int unused;
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extern int unused2[sizeof(unused)];
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