mlx5: unitialized warning

Building current main branch with gcc (Debian 10.2.1-6) 10.2.1 20210110

[1843/3131] Compiling C object drivers/libtmp_rte_net_mlx5.a.p/net_mlx5_mlx5_flow_meter.c.o ../drivers/net/mlx5/mlx5_flow_meter.c: In function ‘mlx5_flow_meter_create’:
../drivers/net/mlx5/mlx5_flow_meter.c:1170:33: warning: ‘legacy_fm’ may be used uninitialized in this function [-Wmaybe-uninitialized]
1170 | struct mlx5_legacy_flow_meter *legacy_fm;
| ^~~~~~~~~

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Building current main branch with gcc (Debian 10.2.1-6) 10.2.1 20210110

[1843/3131] Compiling C object drivers/libtmp_rte_net_mlx5.a.p/net_mlx5_mlx5_flow_meter.c.o ../drivers/net/mlx5/mlx5_flow_meter.c: In function ‘mlx5_flow_meter_create’:
../drivers/net/mlx5/mlx5_flow_meter.c:1170:33: warning: ‘legacy_fm’ may be used uninitialized in this function [-Wmaybe-uninitialized]
1170 | struct mlx5_legacy_flow_meter *legacy_fm;
| ^~~~~~~~~

Hi Stephen,

I don't see this warning with gcc 10.3.0 (Ubuntu 10.3.0-1ubuntu1~20.04). Firstly, I believe it's a false positive:
legacy_fm is initialized and used only when priv->sh->meter_aso_en == false:

1237	if (priv->sh->meter_aso_en) {
		...
1245	} else {
    		legacy_fm = ...
		if (legacy_fm == NULL)
			return ...;
		...
	}
	...
1276	if (!priv->sh->meter_aso_en)
		TAILQ_INSERT_TAIL(fms, legacy_fm, next);

However, even if it's fixed in GCC between 10.2.1 and 10.3.0, I've seen it with x86_64-w64-mingw32-gcc (GCC) 9.3-win32 20200320 while working on enabling drivers/*/mlx5 build with GCC, so a workaround will probably still be needed.

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I don't see this warning with gcc 10.3.0 (Ubuntu 10.3.0-1ubuntu1~20.04).

It maybe because I was testing with thread santizer enabled and compiler was doing different optimizations.

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I don't see this warning with gcc 10.3.0 (Ubuntu 10.3.0-1ubuntu1~20.04).

[...]

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It maybe because I was testing with thread santizer enabled and compiler was doing different optimizations.

Reproduced with -Dc_args=-fsanitize=thread, thanks!