delete-null-pointer-checks

Makefile

all:
	@echo "gcc-4.4 && -fdelete-null-pointer-checks"
	@gcc-4.4 -O2 -ggdb -Wall -Wundef -fno-strict-aliasing -fno-common -fdelete-null-pointer-checks test-deref.c -o test-deref
	@./test-deref || true && 
	@echo "gcc-4.5 && -fdelete-null-pointer-checks"
	@gcc-4.5 -O2 -ggdb -Wall -Wundef -fno-strict-aliasing -fno-common -fdelete-null-pointer-checks test-deref.c -o test-deref
	@./test-deref || true
	@echo "gcc-4.4 && -fno-delete-null-pointer-checks"
	@gcc-4.4 -O2 -ggdb -Wall -Wundef -fno-strict-aliasing -fno-common -fno-delete-null-pointer-checks test-deref.c -o test-deref
	@./test-deref || true
	@echo "gcc-4.5 && -fno-delete-null-pointer-checks"
	@gcc-4.5 -O2 -ggdb -Wall -Wundef -fno-strict-aliasing -fno-common -fno-delete-null-pointer-checks test-deref.c -o test-deref
	@./test-deref || true

test-deref.c

#include <stdio.h>

struct agnx_priv {
    char demo;
};

struct ieee80211_hw {
    struct agnx_priv *priv;
};

struct pci_dev {
    struct ieee80211_hw* dev;
};

struct ieee80211_hw* pci_get_drvdata(struct pci_dev *pdev) {

    if(!pdev)
        return NULL;

    return pdev->dev;
}

static void agnx_pci_remove (struct pci_dev *pdev)
{
    struct ieee80211_hw *dev = pci_get_drvdata(pdev);
    struct agnx_priv *priv = dev->priv;

    if (!dev) return;

    // This will segfault if the previous if is optimized
    printf("%c\n", priv->demo);
}

int main(int argc, char **argv)
{
    // (struct pci_dev *)argv[1] is just to avoid compiler optimisations
    // =~ NULL if no args are passed.
    struct pci_dev * pdev = (struct pci_dev *)argv[1];

    agnx_pci_remove(pdev);
    return 0;
}